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Chaptewr 5 Special Occupancies | 505.6(A) | Atmospheres containing acetylene, hydrogen, or flammable gas, flammable liquid—produced vapor, or combustible liquid—produced vapor mixed with air that may burn or explode, having either a maximum experimental safe gap (MESG) value less than or equal to 0.50 mm or minimum igniting current (MIC) ratio less than or equal to 0.45. [497:3.3.5.2.3] Informational Note: See 500.6(A)(1) and (A)(2) for Class I, Group A and Class I, Group B classifications. Group IIC is equivalent to a combination of Class I, Group A and Class I, Group B. [505.6(A)](https://2023.antflix.net#505.6(A)) | https://2023.antflix.net#505.6(A) |
Chaptewr 5 Special Occupancies | 505.6(B) | Atmospheres containing acetaldehyde, ethylene, or flammable gas, flammable liquid—produced vapor, or combustible liquid—produced vapor mixed with air that may burn or explode, having either maximum experimental safe gap (MESG) values greater than 0.50 mm and less than or equal to 0.90 mm or minimum igniting current ratio (MIC ratio) greater than 0.45 and less than or equal to 0.80. [497:3.3.5.2.2] Informational Note No. 1: See 500.6(A)(3). Class I, Group C is equivalent to Group IIB. Informational Note No. 2: Class I, Group B is equivalent to Group IIB + H2. [505.6(B)](https://2023.antflix.net#505.6(B)) | https://2023.antflix.net#505.6(B) |
Chaptewr 5 Special Occupancies | 505.6(C) | Atmospheres containing acetone, ammonia, ethyl alcohol, gasoline, methane, propane, or flammable gas, flammable liquid—produced vapor, or combustible liquid-produced vapor mixed with air that may burn or explode, having either a maximum experimental safe gap (MESG) value greater than 0.90 mm or minimum igniting current (MIC) ratio greater than 0.80. [497:3.3.5.2.1] Informational Note: See 500.6(A)(4). Class I, Group D is equivalent to Group IIA. [505.6(C)](https://2023.antflix.net#505.6(C)) | https://2023.antflix.net#505.6(C) |
Chaptewr 5 Special Occupancies | 505.7 | This article requires equipment construction and installation that ensures safe performance under conditions of proper use and maintenance. Informational Note No. 1: It is important that inspection authorities and users exercise more than ordinary care regarding the installation and maintenance of electrical equipment in hazardous (classified) locations. Informational Note No. 2: Electrical equipment that is dependent on the protection technique permitted by 505.8(A) might not be suitable for use at temperatures lower than -20°C (-4°F) unless they are identified for use at lower temperatures. Low ambient conditions require special consideration. At low ambient temperatures, flammable concentrations of vapors might not exist in a location classified at normal ambient temperature. [505.7](https://2023.antflix.net#505.7) | https://2023.antflix.net#505.7 |
Chaptewr 5 Special Occupancies | 505.7(A) | Classification of areas, engineering and design, selection of equipment and wiring methods, installation, and inspection shall be performed by qualified persons. [505.7(A)](https://2023.antflix.net#505.7(A)) | https://2023.antflix.net#505.7(A) |
Chaptewr 5 Special Occupancies | 505.7(B) | In instances of areas within the same facility classified separately, Zone 2 locations shall be permitted to abut, but not overlap, Class I, Division 2 locations. Zone 0 or Zone 1 locations shall not abut Class I, Division 1 or Division 2 locations. [505.7(B)](https://2023.antflix.net#505.7(B)) | https://2023.antflix.net#505.7(B) |
Chaptewr 5 Special Occupancies | 505.7(C) | A Class I, Division 1 or Division 2 location shall be permitted to be reclassified as a Zone 0, Zone 1, or Zone 2 location, provided all of the space that is classified because of a single flammable gas or vapor source is reclassified under the requirements of this article. [505.7(C)](https://2023.antflix.net#505.7(C)) | https://2023.antflix.net#505.7(C) |
Chaptewr 5 Special Occupancies | 505.7(D) | Flameproof equipment with flanged joints shall not be installed such that the flange openings are closer than the distances shown in Table 505.7(D) to any solid obstacle that is not a part of the equipment (such as steelworks, walls, weather guards, mounting brackets, pipes, or other electrical equipment) unless the equipment is listed for a smaller distance of separation. [505.7(D)](https://2023.antflix.net#505.7(D)) | https://2023.antflix.net#505.7(D) |
Chaptewr 5 Special Occupancies | 505.7(E) | Where flammable gases, combustible dusts, or fibers/flyings are or may be present at the same time, the simultaneous presence shall be considered during the selection and installation of the electrical equipment and the wiring methods, including the determination of the safe operating temperature of the electrical equipment. [505.7(E)](https://2023.antflix.net#505.7(E)) | https://2023.antflix.net#505.7(E) |
Chaptewr 5 Special Occupancies | 505.7(F) | Unless listed and marked for connection to circuits with higher available fault current, the available fault current for electrical equipment using type of protection "e" for the field wiring connections in Zone 1 locations shall be limited to 10,000 ruts symmetrical amperes to reduce the likelihood of ignition of a flammable atmosphere by an arc during a short-circuit event. Informational Note: Limitation of the available fault current to this level may require the application of current-limiting fuses or current-limiting circuit breakers. Table 505.7(D) Minimum Distance of Obstructions from Flameproof "d" Flange Openings Gas Group Minimum Distance mm in. IIC 40 137/64 IIB 30 13/16 IIA 10 25/64 [505.7(F)](https://2023.antflix.net#505.7(F)) | https://2023.antflix.net#505.7(F) |
Chaptewr 5 Special Occupancies | 505.8 | Acceptable protection techniques for electrical and electronic equipment in hazardous (classified) locations shall be as described in 505.8(A) through (Q). Informational Note No. 1: See ANSI/UL 120101, Definitions and Information Pertaining to Electrical Equipment in Hazardous Locations, and ANSI/UL 60079-0, Explosive Atmospheres - Part 0: Equipment - General Requirements, for additional information. Informational Note No. 2: See Chapter 9, Table 13 for descriptions of subdivisions of protection techniques. [505.8](https://2023.antflix.net#505.8) | https://2023.antflix.net#505.8 |
Chaptewr 5 Special Occupancies | 505.8(A) | This protection technique shall be permitted for equipment in Zone 1 or Zone 2 locations. [505.8(A)](https://2023.antflix.net#505.8(A)) | https://2023.antflix.net#505.8(A) |
Chaptewr 5 Special Occupancies | 505.8(B) | This protection technique shall be permitted for equipment in those Zone 1 or Zone 2 locations for which it is identified. [505.8(B)](https://2023.antflix.net#505.8(B)) | https://2023.antflix.net#505.8(B) |
Chaptewr 5 Special Occupancies | 505.8(C) | This protection technique shall be permitted for apparatus and associated apparatus for Zone 0, Zone 1, or Zone 2 locations for which it is listed. [505.8(C)](https://2023.antflix.net#505.8(C)) | https://2023.antflix.net#505.8(C) |
Chaptewr 5 Special Occupancies | 505.8(D) | This protection technique shall be permitted for equipment in Zone 2 locations. Type of protection "n" is further subdivided into nA, nC, and nR. [505.8(D)](https://2023.antflix.net#505.8(D)) | https://2023.antflix.net#505.8(D) |
Chaptewr 5 Special Occupancies | 505.8(E) | This protection technique shall be permitted for equipment in Zone 1 or Zone 2 locations. [505.8(E)](https://2023.antflix.net#505.8(E)) | https://2023.antflix.net#505.8(E) |
Chaptewr 5 Special Occupancies | 505.8(F) | This protection technique shall be permitted for equipment in Zone 1 or Zone 2 locations. [505.8(F)](https://2023.antflix.net#505.8(F)) | https://2023.antflix.net#505.8(F) |
Chaptewr 5 Special Occupancies | 505.8(G) | This protection technique shall be permitted for equipment in Zone 0, Zone 1, or Zone 2 locations for which it is identified. [505.8(G)](https://2023.antflix.net#505.8(G)) | https://2023.antflix.net#505.8(G) |
Chaptewr 5 Special Occupancies | 505.8(H) | This protection technique shall be permitted for equipment in Zone 1 or Zone 2 locations. [505.8(H)](https://2023.antflix.net#505.8(H)) | https://2023.antflix.net#505.8(H) |
Chaptewr 5 Special Occupancies | 505.8(I) | A detection system for flammable gases shall be permitted as a means of protection in restricted industrial establishments. [505.8(I)](https://2023.antflix.net#505.8(I)) | https://2023.antflix.net#505.8(I) |
Chaptewr 5 Special Occupancies | 505.8(I)(1) | Any gas detection system used as a protection technique shall meet all of the requirements in 505.8(I)(1)(a) through (I)(1)(e). The gas detection equipment used shall be listed for Zone 1 and listed for the detection of the specific gas or vapor to be encountered.The gas detection system shall not use portable or transportable equipment, or temporary wiring methods.The gas detection system shall only use point-type sensors. The system shall be permitted to be augmented with open-path (line-of-sight)—type sensors, but open-path—type sensors shall not be the basis for this protection technique.The type of detection equipment, its listing, the installation location(s), the alarm and shutdown criteria, and the calibration frequency shall be documented where gas detectors are used as a protection technique.The applications for the use of gas detection systems as a protection technique shall be limited to 505.8(1)(2), (I)(3), or (I)(4).Informational Note No. 1: See ANSI/UL 121303, Guide for Use of Detectors for Flammable Gases, or ANSI/FM 121303, Guide for Use of Detectors for Flammable Gases, for additional information.Informational Note No. 2: See ANSI/UL 60079-29-1, Explosive Atmospheres - Part 29-1: Gas Detectors - Performance Requirements of Detectors for Flammable Gases, or ANSI/FM 60079-29-1, Explosive Atmospheres - Part 29-1: Gas Detectors - Performance Requirements of Detectors for Flammable Gases, for additional information.Informational Note No. 3: See ANSI/API RP 505, Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2, for additional information.Informational Note No. 4: See ANSI/UL 60079-29-2, Explosive Atmospheres - Part 29-2: Gas Detectors - Selection, Installation, Use and Maintenance of Detectors for Flammable Gases and Oxygen, or ANSI/FM 60079-29-2, Explosive Atmospheres - Part 29-2: Gas Detectors - Selection, Installation, Use and Maintenance of Detectors for Flammable Gases and Oxygen, for additional information. [505.8(I)(1)](https://2023.antflix.net#505.8(I)(1)) | https://2023.antflix.net#505.8(I)(1) |
Chaptewr 5 Special Occupancies | 505.8(I)(2) | A location, enclosed space, or building that is classified as a Zone 1 location due to inadequate ventilation and that is provided with a detection system for flammable gases shall be permitted to use electrical equipment, installation methods, and wiring practices suitable for Zone 2 installations. Sensing a gas concentration of not more than 40 percent of the lower flammable limit or a gas detector system malfunction shall activate an alarm (audible or visual, or both, as most appropriate for the area). [505.8(I)(2)](https://2023.antflix.net#505.8(I)(2)) | https://2023.antflix.net#505.8(I)(2) |
Chaptewr 5 Special Occupancies | 505.8(I)(3) | Any building or enclosed space that does not contain a source of flammable gas or vapors that is located in, or with an opening into, a Zone 2 hazardous (classified) location that is provided with a detection system for flammable gases shall be permitted to use electrical equipment, installation methods, and wiring practices suitable for unclassified installations under all of the following conditions: An alarm (audible or visual, or both) shall be sounded at not more than 20 percent of the lower flammable limit.Sensing a gas concentration of not more than 40 percent of the lower flammable limit or a gas detector system malfunction shall activate an alarm (audible or visual, or both, as most appropriate for the area) and initiate automatic disconnection of power from all electrical devices in the area that are not suitable for Zone 2.The power disconnecting device(s) shall be suitable for Zone 1 if located inside the building or enclosed space. If the disconnecting device(s) is located outside the building or enclosed space, it shall be suitable for the location in which it is installed.Redundant or duplicate equipment (such as sensors) shall be permitted to be installed to avoid disconnecting electrical power when equipment malfunctions are indicated.When automatic shutdown could introduce additional or increased hazard, this technique shall not be permitted. [505.8(I)(3)](https://2023.antflix.net#505.8(I)(3)) | https://2023.antflix.net#505.8(I)(3) |
Chaptewr 5 Special Occupancies | 505.8(I)(4) | Inside the interior of a control panel containing instrumentation or other equipment using or measuring flammable liquids, gases, or vapors and that is provided with a detection system for flammable gases equipment shall be allowed to use electrical equipment, installation methods, and wiring practices suitable for Zone 2 installations. An alarm (audible or visual, or both) shall be sounded at not more than 40 percent of the lower flammable limit. [505.8(I)(4)](https://2023.antflix.net#505.8(I)(4)) | https://2023.antflix.net#505.8(I)(4) |
Chaptewr 5 Special Occupancies | 505.8(J) | "60079-30-1". This protection technique shall be permitted for electrical resistance trace heating equipment in Zone 1 or Zone 2 for which it is listed. [505.8(J)](https://2023.antflix.net#505.8(J)) | https://2023.antflix.net#505.8(J) |
Chaptewr 5 Special Occupancies | 505.8(K) | This protection technique shall be permitted for equipment in Zone 0, Zone 1, or Zone 2 locations for which the equipment is identified. [505.8(K)](https://2023.antflix.net#505.8(K)) | https://2023.antflix.net#505.8(K) |
Chaptewr 5 Special Occupancies | 505.8(L) | This protection technique shall be permitted for equipment in Zone 1 or Zone 2 locations for which the equipment is identified. [505.8(L)](https://2023.antflix.net#505.8(L)) | https://2023.antflix.net#505.8(L) |
Chaptewr 5 Special Occupancies | 505.8(M) | This protection technique shall be permitted for equipment in Zone 0, Zone 1, or Zone 2 locations for which the equipment is identified. [505.8(M)](https://2023.antflix.net#505.8(M)) | https://2023.antflix.net#505.8(M) |
Chaptewr 5 Special Occupancies | 505.8(N) | This protection technique shall be permitted for skin effect trace heating equipment in Zone 1 or Zone 2 locations for which it is listed. [505.8(N)](https://2023.antflix.net#505.8(N)) | https://2023.antflix.net#505.8(N) |
Chaptewr 5 Special Occupancies | 505.8(O) | This protection technique shall be permitted for impedance heating of pipelines, and equipment in Zone 2 locations for which it is listed. [505.8(O)](https://2023.antflix.net#505.8(O)) | https://2023.antflix.net#505.8(O) |
Chaptewr 5 Special Occupancies | 505.8(P) | This protection technique shall be permitted for equipment in Zone 1 or Zone 2 locations for which it is identified. [505.8(P)](https://2023.antflix.net#505.8(P)) | https://2023.antflix.net#505.8(P) |
Chaptewr 5 Special Occupancies | 505.8(Q) | This protection technique shall be permitted for equipment in Zone 0, Zone 1, or Zone 2 locations for which it is listed. [505.8(Q)](https://2023.antflix.net#505.8(Q)) | https://2023.antflix.net#505.8(Q) |
Chaptewr 5 Special Occupancies | 505.9(A) | Suitability of identified equipment shall be determined by one of the following: Equipment listing or labelingEvidence of equipment evaluation from a qualified testing laboratory or inspection agency concerned with product evaluationEvidence acceptable to the authority having jurisdiction such as a manufacturer's self-evaluation or an owner's engineering judgmentInformational Note: Additional documentation for equipment may include certificates demonstrating compliance with applicable equipment standards, indicating special conditions of use, and other pertinent information. [505.9(A)](https://2023.antflix.net#505.9(A)) | https://2023.antflix.net#505.9(A) |
Chaptewr 5 Special Occupancies | 505.9(B) | Equipment that is listed for a Zone 0 location shall be permitted in a Zone 1 or Zone 2 location of the same gas or vapor, provided that it is installed in accordance with the requirements for the marked type of protection. Equipment that is listed for a Zone 1 location shall be permitted in a Zone 2 location of the same gas or vapor, provided that it is installed in accordance with the requirements for the marked type of protection.Equipment shall be permitted to be listed for a specific gas or vapor, specific mixtures of gases or vapors, or any specific combination of gases or vapors.Informational Note: One common example is equipment marked for "IIB. + H2." [505.9(B)](https://2023.antflix.net#505.9(B)) | https://2023.antflix.net#505.9(B) |
Chaptewr 5 Special Occupancies | 505.9(C) | Equipment shall be marked in accordance with 505.9(C)(1) or (C)(2). [505.9(C)](https://2023.antflix.net#505.9(C)) | https://2023.antflix.net#505.9(C) |
Chaptewr 5 Special Occupancies | 505.9(C)(1) | Equipment identified for Class I, Division 1 or Class I, Division 2 shall, in addition to being marked in accordance with 500.8(C), be permitted to be marked with all of the following: Class I, Zone 1 or Zone 1; Class I, Zone 2 or Zone 2 (as applicable)Applicable gas classification group(s) in accordance with Table 505.9(C)(1)Temperature classification in accordance with 505.9(D) [505.9(C)(1)](https://2023.antflix.net#505.9(C)(1)) | https://2023.antflix.net#505.9(C)(1) |
Chaptewr 5 Special Occupancies | 505.9(C)(2) | Equipment meeting one or more of the protection techniques described in 505.8 shall be marked with all of the following in the order shown: Class I shall be an optional marking. If it is included in the equipment marking, the Class I marking shall precede the zone marking.Zone in accordance with Chapter 9, Table 13.Symbol "AEx".Protection technique(s) in accordance with Chapter 9, Table 13.Applicable material group in accordance with Table 505.9(C)(1) or a specific gas or vapor.Temperature classification in accordance with 505.9(D).Equipment protection level (EPL).Exception No. 1: Associated apparatus NOT suitable for installation in a hazardous (classified) location shall be required to be marked only with 505.9(C)(2)(3), (C)(2)(4), and (C)(2)(5), but BOTH the symbol AEx (3) and the symbol for the type of protection (4) shall be enclosed within the same square brackets, for example, [AEx ia Ga] IIC.Exception No. 2: Simple apparatus as defined in Article 100 shall not be required to have a marked operating temperature or temperature class.Exception No. 3: Fittings for the termination of cables shall not be required to have a marked operating temperature or temperature class.Informational Note No. 1: See Informational Note Figure 505.9(C)(2), for an explanation of the marking that is required. An example of the required marking for intrinsically safe apparatus for installation in Zone 0 is "Class I, Zone 0, AEx ia IIC T6 Ga" or "Zone 0, AEx, ia, IIC T6 Gb."Informational Note No. 2: An example of the required marking for intrinsically safe associated apparatus mounted in a flameproof enclosure for installation in Zone 1 is "Class I, Zone 1 AEx db[ia] IIC T4 Gb" or "Zone 1, AEx, db[ia Ga] IIC T4 Gb."Informational Note No. 3: An example of the required marking for intrinsically safe associated apparatus NOT for installation in a hazardous (classified) location is "[AEx ia Ga] IIC."Informational Note No. 4: EPLs are designated as G for gas, or D for dust, and are then followed by a letter (a, b, or c) to give the user a better understanding as to whether the equipment provides (a) a "very high," (b) a "high," or (c) an "enhanced" level of protection against ignition of an explosive atmosphere. For example, a Zone 1, AEx db IIC T4 Gb motor (which is suitable by protection concept for application in Zone 1) is marked with an EPL of "Gb" to indicate that it was provided with a high level of protection.Informational Note No. 5: See ANSI/UL 60079-26, Explosive Atmospheres - Part 26: Equipment with Equipment Protection Level (EPL) Ga, for additional information. Equipment installed outside a Zone 0 location and electrically connected to equipment located inside a Zone 0 location might be marked Zone 0/1. The "/" indicates that equipment contains a separation element and can be installed at the boundary between a Zone 0 and a Zone 1 location. [505.9(C)(2)](https://2023.antflix.net#505.9(C)(2)) | https://2023.antflix.net#505.9(C)(2) |
Chaptewr 5 Special Occupancies | 505.9(D) | The temperature marking shall not exceed the autoignition temperature of the specific gas or vapor to be encountered. Informational Note No. 1: See ANSI/UL 60079-26, Explosive Atmospheres - Part 26: Equipment with Equipment Protection Level (EPL) Ga, for more information. Equipment installed outside a Zone 0 location and electrically connected to equipment located inside a Zone 0 location might be marked Zone 0/1. The "/'' indicates that equipment contains a separation element and can be installed at the boundary between a Zone 0 and a Zone 1 location. Equipment shall be marked to show the operating temperature or temperature class referenced to a 40°C ambient, or at the higher ambient temperature if the equipment is rated and marked for an ambient temperature of greater than 40°C. The temperature class, if provided, shall be indicated using the temperature class (T code) shown in Table 505.9(D). Informational Note Figure 505.9(C)(2) Zone Equipment Marking. Electrical equipment designed for use in the ambient temperature range between —20°C and +40°C shall require no ambient temperature marking. Electrical equipment that is designed for use in a range of ambient temperatures other than —20°C to +40°C is considered to be special; and the ambient temperature range shall then be marked on the equipment, including either the symbol "Ta" or "Tamb" together with the special range of ambient temperatures, in degrees Celsius. Informational Note No. 2: For example, such a marking might be "—30°C to +40°C." Exception No. 1: Equipment of the non-heat-producing type, such as conduit fittings, and equipment of the heat-producing type having a maximum temperature of not more than 100°C (212°F) shall not be required to have a marked operating temperature or temperature class. Exception No. 2: Equipment identified for Class I, Division 1 or Division 2 locations as permitted by 505.20(A), (B), and (C) shall be permitted to be marked in accordance with 505.8(C) and Table 500.8(C)(4). [505.9(D)](https://2023.antflix.net#505.9(D)) | https://2023.antflix.net#505.9(D) |
Chaptewr 5 Special Occupancies | 505.9(E) | The supply connection entry thread form shall be NPT or metric. Conduit and fittings shall be made wrench-tight to prevent sparking when fault current flows through the conduit system, and to ensure the explosionproof or flameproof integrity of the conduit system where applicable. Equipment provided with threaded entries for field wiring connections shall be installed in accordance with 505.9(E)(1) or (E)(2) and with (E)(3). [505.9(E)](https://2023.antflix.net#505.9(E)) | https://2023.antflix.net#505.9(E) |
Chaptewr 5 Special Occupancies | 505.9(E)(1) | For equipment provided with threaded entries for NPT threaded conduit or fittings, listed conduit, listed conduit fittings, or listed cable fittings shall be used. All NPT threaded conduit and fittings shall be threaded with a National (American) Standard Pipe Taper (NPT) thread. NPT threaded entries into explosionproof or flameproof equipment shall be made up with at least five threads fully engaged. Exception: For listed explosionproof or flameproof equipment, factory-threaded NPT entries shall be made up with at least 41/2 threads fully engaged. Informational Note No. 1: See ASME B1.20.1, Pipe Threads, General Purpose (Inch), for thread specifications for male NPT threads. Informational Note No. 2: See ANSI/UL 60079-1, Explosive Atmospheres - Part 1: Equipment Protection by Flameproof Enclosures"d", and ASME B1.20.1, Pipe Threads, General Purpose (Inch), for information on female NPT threaded entries using modified National Standard Pipe Taper (NPT) thread. [505.9(E)(1)](https://2023.antflix.net#505.9(E)(1)) | https://2023.antflix.net#505.9(E)(1) |
Chaptewr 5 Special Occupancies | 505.9(E)(2) | For equipment with metric threaded entries, listed conduit fittings or listed cable fittings shall be used. Such entries shall be identified as being metric, or listed adapters to permit connection to conduit or NPT threaded fittings shall be provided with the equipment and shall be used for connection to conduit or NPT threaded fittings. Metric threaded fittings installed into explosionproof or flameproof equipment entries shall have a class of fit of at least 6g/6H and be made up with at least five threads fully engaged. Informational Note: See ISO 965-1, ISO general purpose metric screw threads - Tolerances - Part 1: Principles and basic data, and ISO 965-3, ISO general purpose metric screw threads - Tolerances - Part 3: Deviations for constructional screw threads, for threading specifications for metric threaded entries. [505.9(E)(2)](https://2023.antflix.net#505.9(E)(2)) | https://2023.antflix.net#505.9(E)(2) |
Chaptewr 5 Special Occupancies | 505.9(E)(3) | All unused openings shall be closed with blanking elements or close-up plugs that are listed for the location and will maintain the type of protection. Thread engagement shall comply with 505.9(E)(1) or (E)(2). [505.9(E)(3)](https://2023.antflix.net#505.9(E)(3)) | https://2023.antflix.net#505.9(E)(3) |
Chaptewr 5 Special Occupancies | 505.9(F) | An optical fiber cable, with or without current-carrying conductors (hybrid optical fiber cable), shall be installed to address the associated fire hazard and sealed to address the associated explosion hazard in accordance with 505.15 and 505.16. [505.9(F)](https://2023.antflix.net#505.9(F)) | https://2023.antflix.net#505.9(F) |
Chaptewr 5 Special Occupancies | 505.9(G) | For equipment involving sources of optical radiation (such as laser or LED sources) in the wavelength range from 380 nm to 10 pm, the risk of ignition from optical radiation shall be considered for all electrical parts and circuits that may be exposed to the radiation, both inside and outside the optical equipment. This includes optical equipment, which itself is located outside the explosive atmosphere, but its emitted optical radiation enters such atmospheres. Informational Note: See ANSI/UL 60079-28, Explosive Atmospheres - Part 28: Protection of Equipment and Transmission Systems Using Optical Radiation, for information on types of protection to minimize the risk of ignition in explosive atmospheres from optical radiation. Exception: All luminaires (fixed, portable, or transportable) and hand lights, intended to be supplied by mains (with or without galvanic isolation) or powered by batteries, with any continuous divergent light source, including LEDs, shall be excluded from this requirement. Table 505.9(C)(1) Material Groups Material Group Comment IIC See 505.6(A) IIB See 505.6(B) IIA See 505.6(C) Table 505.9(D) Temperature Classification Marking of Maximum Surface Temperature for Group II Electrical Equipment Temperature Class(T Code) Maximum Surface Temperature(°C) T1 ≤450 T2 ≤300 T3 ≤200 T4 ≤135 T5 ≤100 T6 ≤85 [505.9(G)](https://2023.antflix.net#505.9(G)) | https://2023.antflix.net#505.9(G) |
Chaptewr 5 Special Occupancies | 505.15 | Wiring methods shall maintain the integrity of protection techniques and shall comply with 505.15(A) through (C). [505.15](https://2023.antflix.net#505.15) | https://2023.antflix.net#505.15 |
Chaptewr 5 Special Occupancies | 505.15(A) | In Zone 0 locations, equipment protected by intrinsic safety "ia" and equipment protected by encapsulation "ma" shall be connected using intrinsically safe "ia" circuits with wiring methods in accordance with 504.20. [505.15(A)](https://2023.antflix.net#505.15(A)) | https://2023.antflix.net#505.15(A) |
Chaptewr 5 Special Occupancies | 505.15(B)(1) | In Zone 1 locations, the following wiring methods shall be permitted: Informational Note No. 1: See Article 100 for the definition of restricted industrial establishment [as applied to hazardous (classified) locations].All wiring methods permitted by 505.15(A).In restricted industrial establishments where the cable is not subject to physical damage, Type MC-HL cable listed for use in Zone 1 or Class I, Division 1 locations, with a gas/vaportight continuous corrugated metallic sheath, an overall jacket of suitable polymeric material, and a separate equipment grounding conductor(s) in accordance with 250.122. Type MC-HL cable shall be terminated with fittings listed for the application and installed in accordance with Part II of Article 330.In restricted industrial establishments where the cable is not subject to physical damage, Type ITC-HL cable listed for use in Zone 1 or Class I, Division 1 locations, with a gas/vaportight continuous corrugated metallic sheath and an overall jacket of suitable polymeric material. Type ITC-HL cable shall be terminated with fittings listed for the application and installed in accordance with 335.4Type MI cable terminated with fittings listed for Zone 1 or Class I, Division 1 locations. Type MI cable shall be installed and supported in a manner to avoid tensile stress at the termination fittings.Threaded rigid metal conduit (RMC) or threaded intermediate metal conduit (IMC), including RMC or IMC conduit systems with supplemental corrosion protection coatings.Where encased in a concrete envelope a minimum of 50 mm (2 in.) thick and provided with not less than 600 mm (24 in.) of cover measured from the top of the conduit to grade, PVC or RTRC conduit. RMC or IMC conduit shall be used for the last 600 mm (24 in.) of the underground run to emergence or to the point of connection to the aboveground raceway. An equipment grounding conductor shall be included to provide for electrical continuity of the raceway system and for grounding of non—current-carrying metal parts.Intrinsic safety type of protection "ib" using the wiring methods in accordance with 504.20.Optical fiber cable Type OFNP, Type OFCP, Type OFNR, Type OFCR, Type OFNG, Type OFCG, Type OFN, or Type OFC installed in raceways in accordance with 505.15(B). Optical fiber cable shall be sealed in accordance with 505.16.In restricted industrial establishments for applications limited to 600 volts nominal or less where the cable is not subject to physical damage, Type TC-ER-HL shall be terminated with fittings listed for the location and installed in accordance with 336.10.Informational Note No. 2: See ANSI/UL 2225, Cables and Cable-Fittings for Use in Hazardous (Classified) Locations, for information on construction, testing, and marking of cables and cable fittings.In restricted industrial establishments, listed Type P cable with metal braid armor and an overall jacket. Type P cable shall be terminated with fittings listed for the location and installed in accordance with Part II of Article 337.Informational Note No. 3: See UL 1309A, Outline of Investigation for Cable for use in Mobile Installations, for information on construction, testing, and marking of Type P cable.Informational Note No. 4: See ANSI/UL 2225, Cables and Cable-Fittings for Use in Hazardous (Classified) Locations, for information on construction, testing, and marking of cable fittings. [505.15(B)(1)](https://2023.antflix.net#505.15(B)(1)) | https://2023.antflix.net#505.15(B)(1) |
Chaptewr 5 Special Occupancies | 505.15(B)(2) | If flexibility is necessary to minimize the transmission of vibration from equipment during operation or to allow for movement after installation during maintenance, one of the following shall be permitted: Flexible fittings listed for the location.Flexible cord in accordance with 505.17(A), terminated with cord connectors listed for the location.In restricted industrial establishments for applications limited to 600 volts nominal or less, where the cable is not subject to physical damage and is terminated with fittings listed for the location, Type TC-ER-HL cable. Type TC-ER-HL cable shall be listed for use in Class I, Division 1 or Zone 1 locations and shall be installed in accordance with 336.10.Informational Note No. 1: See ANSI/UL 2225, Cables and Cable-Fittings for Use in Hazardous (Classified) Locations, for information on construction, testing, and marking of cables and cable fittings.In restricted industrial establishments listed Type P cable with metal braid armor and an overall jacket. Type P cable shall be terminated with fittings listed for the location and installed in accordance with Part II of Article 337.Informational Note No. 2: See UL 1309A, Outline of Investigation for Cable for Use in Mobile Installations, for information on construction, testing, and marking of Type P cable.Informational Note No. 3: See ANSI/UL 2225, Cables and Cable-Fittings for Use in Hazardous (Classified) Locations, for information on construction, testing, and marking of cable fittings. [505.15(B)(2)](https://2023.antflix.net#505.15(B)(2)) | https://2023.antflix.net#505.15(B)(2) |
Chaptewr 5 Special Occupancies | 505.15(C)(1) | In Zone 2 locations, the following wiring methods shall be permitted: Informational Note No. 1: See Article 100 for the definition of restricted industrial establishment [as applied to hazardous (classified) locations].All wiring methods permitted by 505.15(B).Type MCI, Type MV, Type TC, or Type TC-ER cable, including installation in cable tray systems. Type TC-ER shall include a separate equipment grounding conductor in addition to a drain wire that might be present. The cable shall be terminated with listed fittings. Single conductor Type MV cables shall be shielded or metallic-armored.Type ITC cable or Type ITC-ER cable as permitted in 335.4 and terminated with listed fittings. Type ITC-ER shall include a separate insulated equipment grounding conductor in addition to a drain wire.Type PLTC cable or Type PLTC-ER cable used for Class 2 or Class 3 circuits, including installation in cable tray systems. The cable shall be terminated with listed fittings. Type PLTC-ER shall include a separate insulated equipment grounding conductor in addition to a drain wire that might be present.Enclosed gasketed busways or enclosed gasketed wire-ways.In restricted industrial establishments and where metal conduit does not provide the corrosion resistance needed for the environment where it is installed, listed reinforced thermosetting resin conduit (RTRC), factory elbows, and associated fittings, all marked with the suffix -XW, and Schedule 80 PVC conduit, factory elbows, and associated fittings. Where seals are required for boundary conditions as defined in 505.16(C)(1)(b), the Zone 1 wiring method shall extend into the Zone 2 area to the seal, which shall be located on the Zone 2 side of the Zone 1/Zone 2 boundary.Intrinsic safety type of protection "ic" using any of the wiring methods permitted for unclassified locations. Intrinsic safety type of protection "ic" systems shall be installed in accordance with the control drawing(s). Simple apparatus, not shown on the control drawing, shall be permitted in an intrinsic safety type of protection "ic" circuit if the simple apparatus does not interconnect the intrinsic safety type of protection "ic" systems to any other circuit. Separate intrinsic safety type of protection "ic" systems shall be installed in accordance with one of the following:In separate cablesIn multiconductor cables where the conductors of each circuit are within a grounded metal shieldIn multiconductor cables where the conductors of each circuit have insulation with a minimum thickness of 0.25 mm (0.01 in.)Informational Note No. 2: See Article 100 for the definition of simple apparatus.Optical fiber cable of Type OFNP, Type OFCP, Type OFNR, Type OFCR, Type OFNG, Type OFCG, Type OFN, or Type OFC installed in cable trays or any other raceway in accordance with 505.15(C). Optical fiber cable shall be sealed in accordance with 505.16.Cablebus.In restricted industrial establishments, listed Type P cable with or without metal braid armor and an overall jacket. Type P cable shall be terminated with fittings listed for the location and installed in accordance with Part II of Article 337.Informational Note No. 3: See UL 1309A, Outline of Investigation for Cable for Use in Mobile Installations, for information on construction, testing, and marking of Type P cable.Informational Note No. 4: See ANSI/UL 2225, Cables and Cable-Fittings for Use in Hazardous (Classified) Locations, for information on construction, testing, and marking of cable fittings. [505.15(C)(1)](https://2023.antflix.net#505.15(C)(1)) | https://2023.antflix.net#505.15(C)(1) |
Chaptewr 5 Special Occupancies | 505.15(C)(2) | Where flexibility is necessary to minimize the transmission of vibration from equipment during operation or to allow for movement after installation during maintenance, one or more of the following wiring methods shall be permitted: Listed flexible metal fittingsFlexible metal conduit with listed fittingsInterlocked armor Type MC cable with listed fittingsType P cableType TC-ER or Type TC-ER-HL cableType ITC-ER or Type ITC-HL cableType PLTC-ER cableLiquidtight flexible metal conduit with listed fittingsLiquidtight flexible nonmetallic conduit with listed fittingsFlexible cord in accordance with 505.17, terminated with a listed cord connector that maintains the type of protection of the terminal compartmentFor elevator use, an identified elevator cable of Type EO, Type ETP, or Type ETT, shown under the "use" column in Table 400.4 for "hazardous (classified) locations" and terminated with listed fittingsIf flexible conduit is used, it shall be grounded in accordance with 505.30(A) and bonded in accordance with 505.30(B). [505.15(C)(2)](https://2023.antflix.net#505.15(C)(2)) | https://2023.antflix.net#505.15(C)(2) |
Chaptewr 5 Special Occupancies | 505.16 | Seals in conduit and cable systems shall comply with 505.16(A) through (E). Sealing compound shall be used in Type MI cable termination fittings to exclude moisture and other fluids from the cable insulation. Informational Note No. 1: See 505.16(C)(2)(c). Seals are provided in conduit and cable systems to minimize the passage of gases and vapors and prevent the passage of flames from one portion of the electrical installation to another through the conduit. Such communication through Type VII cable is inherently prevented by construction of the cable. Unless specifically designed and tested for the purpose, conduit and cable seals are not intended to prevent the passage of liquids, gases, or vapors at a continuous pressure differential across the seal. Even at differences in pressure across the seal equivalent to a few inches of water, there might be a slow passage of gas or vapor through a seal and through conductors passing through the seal. Informational Note No. 2: See 505.16(D)(2). Temperature extremes and highly corrosive liquids and vapors can affect the ability of seals to perform their intended function. Informational Note No. 3: Gas or vapor leakage and propagation of flames might occur through the interstices between the strands of standard stranded conductors larger than 2 AWG. Special conductor constructions, for example, compacted strands or sealing of the individual strands, are means of reducing leakage and preventing the propagation of flames. [505.16](https://2023.antflix.net#505.16) | https://2023.antflix.net#505.16 |
Chaptewr 5 Special Occupancies | 505.16(A) | In Zone 0 locations, seals shall be located according to 505.16(A)(1), (A)(2), and (A)(3). [505.16(A)](https://2023.antflix.net#505.16(A)) | https://2023.antflix.net#505.16(A) |
Chaptewr 5 Special Occupancies | 505.16(A)(1) | Seals shall be provided within 3.05 m (10 ft) of where a conduit leaves a Zone 0 location. There shall be no unions, couplings, boxes, or fittings, except listed reducers at the seal, in the conduit run between the seal and the point at which the conduit leaves the location. Exception: A rigid unbroken conduit that passes completely through the Zone 0 location with no fittings less than 300 mm (12 in.) beyond each boundary shall not be required to be sealed if the termination points of the unbroken conduit are in unclassified locations. [505.16(A)(1)](https://2023.antflix.net#505.16(A)(1)) | https://2023.antflix.net#505.16(A)(1) |
Chaptewr 5 Special Occupancies | 505.16(A)(2) | Seals shall be provided on cables at the first point of termination after entry into the Zone 0 location. [505.16(A)(2)](https://2023.antflix.net#505.16(A)(2)) | https://2023.antflix.net#505.16(A)(2) |
Chaptewr 5 Special Occupancies | 505.16(A)(3) | Seals shall not be required to be explosionproof or flameproof. [505.16(A)(3)](https://2023.antflix.net#505.16(A)(3)) | https://2023.antflix.net#505.16(A)(3) |
Chaptewr 5 Special Occupancies | 505.16(B) | In Zone 1 locations, seals shall be located in accordance with 505.16(B)(1) through (B)(8). [505.16(B)](https://2023.antflix.net#505.16(B)) | https://2023.antflix.net#505.16(B) |
Chaptewr 5 Special Occupancies | 505.16(B)(1) | Conduit seals shall be provided within 50 mm (2 in.) for each conduit entering enclosures having type of protection "d", "db", "e", or "eb". Exception No. 1: Where the enclosure having type of protection "d" or "db" is marked to indicate that a seal is not required. Exception No. 2: For type of protection "e" or "eb", conduit and fittings employing only NPT to NPT raceway joints or fittings listed for type of protection "e" or "eb" shall be permitted between the enclosure and the seal, and the seal shall not be required to be within 50 mm (2 in.) of the entry. Informational Note: Examples of fittings employing other than NPT threads include conduit couplings, capped elbows, unions, and breather drains. Exception No. 3: For conduit installed between type of protection "e" or "eb" enclosures employing only NPT to NPT raceway joints or conduit fittings listed for type of protection "e" or "eb", a seal shall not be required. [505.16(B)(1)](https://2023.antflix.net#505.16(B)(1)) | https://2023.antflix.net#505.16(B)(1) |
Chaptewr 5 Special Occupancies | 505.16(B)(2) | Conduit seals shall be provided for each conduit entering explosionproof equipment according to 505.16(B)(2)(a), (B)(2)(b), and (B)(2)(c). In each conduit entry into an explosionproof enclosure where either of the following conditions apply:The enclosure contains apparatus, such as switches, circuit breakers, fuses, relays, or resistors that may produce arcs, sparks, or high temperatures that are considered to be an ignition source in normal operation. For the purposes of this section, high temperatures shall be considered to be any temperatures exceeding 80 percent of the autoignition temperature in degrees Celsius of the gas or vapor involved.Exception: Seals shall not be required for conduit entering an enclosure where such switches, circuit breakers, fuses, relays, or resistors comply with one of the following:Are enclosed within a chamber hermetically sealed against the entrance of gases or vapors.Are immersed in oil.Are enclosed within an enclosure, identified for the location, and marked. "Leads Factory Sealed," "Factory Sealed," "Seal not Required," or equivalent.The entry is metric designator 53 (trade size 2) or larger and the enclosure contains terminals, splices, or taps.An enclosure, identified for the location, and marked "Leads Factory Sealed," or "Factory Sealed," Seal not Required," or equivalent shall not be considered to serve as a seal for another adjacent explosionproof enclosure that is required to have a conduit seal.Conduit seals shall be installed within 450 mm (18 in.) from the enclosure. Only threaded couplings, or explosionproof fittings such as unions, reducers, elbows, and capped elbows that are not larger than the trade size of the conduit, shall be permitted between the sealing fitting and the explosionproof enclosure.Where two or more explosionproof enclosures for which conduit seals are required under 505.16(B)(2) are connected by nipples or by runs of conduit not more than 900 mm (36 in.) long, a single conduit seal in each such nipple connection or run of conduit shall be considered sufficient if located not more than 450 mm (18 in.) from either enclosure. [505.16(B)(2)](https://2023.antflix.net#505.16(B)(2)) | https://2023.antflix.net#505.16(B)(2) |
Chaptewr 5 Special Occupancies | 505.16(B)(3) | Conduit seals shall be provided in each conduit entry into a pressurized enclosure or pressurized room where the conduit is not pressurized as part of the protection system. Conduit seals shall be installed within 450 mm (18 in.) from the pressurized enclosure or pressurized room. Informational Note No. 1: Installing the seal as close as possible to the enclosure reduces problems with purging the dead airspace in the pressurized conduit. Informational Note No. 2: See NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment, for information on pressurized equipment. Informational Note No. 3: See UL 60079-13, Explosive Atmospheres - Part 13: Equipment Protection by Pressurized Room "p" and Artificially Ventilated Room "v", for additional information. [505.16(B)(3)](https://2023.antflix.net#505.16(B)(3)) | https://2023.antflix.net#505.16(B)(3) |
Chaptewr 5 Special Occupancies | 505.16(B)(4) | Conduit seals shall be provided in each conduit run leaving a Zone 1 location. The sealing fitting shall be permitted on either side of the boundary of such location within 3.05 m (10 ft) of the boundary and shall be designed and installed so as to minimize the amount of gas or vapor within the Zone 1 portion of the conduit from being communicated to the conduit beyond the seal. Except for listed explosionproof reducers at the conduit seal, there shall be no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Zone 1 location. Exception: Metal conduit containing no unions, couplings, boxes, or fittings and passing completely through a Zone 1 location with no fittings less than 300 mm (12 in.) beyond each boundary shall not require a conduit seal if the termination points of the unbroken conduit are in unclassified locations. [505.16(B)(4)](https://2023.antflix.net#505.16(B)(4)) | https://2023.antflix.net#505.16(B)(4) |
Chaptewr 5 Special Occupancies | 505.16(B)(5) | Conduits containing cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall be sealed in the Zone 1 location after removing the jacket and any other coverings so that the sealing compound surrounds each individual insulated conductor or optical fiber tube and the outer jacket. Exception: Multiconductor cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall be permitted to be considered as a single conductor by sealing the cable in the conduit within 450 mm (18 in.) of the enclosure and the cable end within the enclosure by an approved means to minimize the entrance of gases or vapors and prevent the propagation of flame into the cable core, or by other approved methods. For shielded cables and twisted pair cables, it shall not be required to remove the shielding material or separate the twisted pair. [505.16(B)(5)](https://2023.antflix.net#505.16(B)(5)) | https://2023.antflix.net#505.16(B)(5) |
Chaptewr 5 Special Occupancies | 505.16(B)(6) | Each multiconductor or optical multifiber cable in conduit shall be considered as a single conductor or single optical fiber tube if the cable is incapable of transmitting gases or vapors through the cable core. These cables shall be sealed in accordance with 505.16(D). [505.16(B)(6)](https://2023.antflix.net#505.16(B)(6)) | https://2023.antflix.net#505.16(B)(6) |
Chaptewr 5 Special Occupancies | 505.16(B)(7) | Cable seals shall be provided for each cable entering flameproof or explosionproof enclosures. The seal shall comply with 505.16(D). [505.16(B)(7)](https://2023.antflix.net#505.16(B)(7)) | https://2023.antflix.net#505.16(B)(7) |
Chaptewr 5 Special Occupancies | 505.16(B)(8) | Cables shall be sealed at the point at which they leave the Zone 1 location. Exception: Where cable is sealed at the termination point. [505.16(B)(8)](https://2023.antflix.net#505.16(B)(8)) | https://2023.antflix.net#505.16(B)(8) |
Chaptewr 5 Special Occupancies | 505.16(C) | In Zone 2 locations, seals shall be installed in accordance with 505.16(C)(1) and (C)(2). [505.16(C)](https://2023.antflix.net#505.16(C)) | https://2023.antflix.net#505.16(C) |
Chaptewr 5 Special Occupancies | 505.16(C)(1) | Conduit seals shall be provided in accordance with 505.16(C)(1)(a) through (C)(1)(f). Flameproof and Explosionproof Enclosures. Conduit seals shall be required for connections to enclosures that are required to be flameproof or explosionproof, in accordance with 505.16(B)(1) and (B)(2). All portions of the conduit run or nipple between the seal and enclosure shall comply with 505.16(B).Conduits Between Zone 2 and Unclassified Locations. Conduit seals shall be required in each conduit run passing from a Zone 2 location into an unclassified location. The conduit seals and conduit run shall comply with all the following:The sealing fitting shall be permitted on either side of the boundary of the location within 3.05 m (10 ft) of the boundary.The sealing fitting shall be designed and installed to minimize the amount of gas or vapor within the Zone 2 portion of the conduit from being communicated to the conduit beyond the seal.Threaded rigid metal conduit (RMC) or threaded intermediate metal conduit (IMC) shall be used between the sealing fitting and the point at which the conduit leaves the Zone 2 location, and a threaded connection shall be used at the sealing fitting.There shall be no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Zone 2 location except for listed explosionproof reducers at the conduit seal.Conduits shall be sealed to minimize the amount of gas or vapor within the Zone 2 portion of the conduit from being communicated to the conduit beyond the seal.Such seals shall not be required to be flameproof or explosionproof but shall be identified for the purpose of minimizing passage of gases under normal operating conditions and shall be accessible.Conduits Passing Through a Zone 2 Location. Metal conduit containing no unions, couplings, boxes, or fittings and passing completely through a Zone 2 location with no fittings less than 300 mm (12 in.) beyond each boundary shall not be required to be sealed if the termination points of the unbroken conduit are in unclassified locations.Conduit Systems Ending in an Unclassified Location. Conduit systems terminating in an unclassified location where a wiring method transition is made to cable tray, cablebus, ventilated busway, Type MI cable, or cable that is not installed in a raceway or cable tray system shall not be required to be sealed where passing from the Zone 2 location into the unclassified location. The unclassified location shall be outdoors or, if the conduit system is all in one room, it shall be permitted to be indoors. The conduits shall not terminate at an enclosure containing an ignition source in normal operation.Pressurized Enclosures or Pressurized Rooms. Conduit systems passing from enclosures or rooms that permit general-purpose equipment as a result of pressurization into a Zone 2 location shall not require a seal at the boundary.Informational Note: See NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment, for information on purged and pressurized equipment.Outdoor Conduit System Segments. Segments of above-ground conduit systems shall not be required to be sealed where passing from a Zone 2 location into an unclassified location if all the following conditions are met:The conduit system segment shall not pass through a Zone 0 or Zone 1 location where the conduit contains unions, couplings, boxes, or fittings within 300 mm (12 in.) of the Zone 0 or Zone 1 location.The conduit system segment shall be located entirely in an outdoor location.The conduit system segment shall not be directly connected to canned pumps, process or service connections for flow, pressure, or analysis measurement, and so forth, that depend on a single compression seal, diaphragm, or tube to prevent flammable or combustible fluids from entering the conduit system.The conduit system segment shall only have threaded rigid metal conduit (RMC) and threaded intermediate metal conduit (IMC) with threaded unions, couplings, conduit bodies, and fittings in the unclassified location.The conduit system segment shall be sealed at its entry to each enclosure or fitting housing terminals, splices, or taps in Zone 2 locations. [505.16(C)(1)](https://2023.antflix.net#505.16(C)(1)) | https://2023.antflix.net#505.16(C)(1) |
Chaptewr 5 Special Occupancies | 505.16(C)(2) | Cable seals shall be installed in accordance with 505.16(C)(2)(a) through (C)(2)(c). Explosionproof and Flameproof Enclosures. Cables entering enclosures required to be flameproof or explosionproof shall be sealed at the point of entrance. The seal shall comply with 505.16(D). Multiconductor or optical multifiber cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall be sealed in the Zone 2 location after removing the jacket and any other coverings so that the sealing compound surrounds each individual insulated conductor or optical fiber tube to minimize the passage of gases and vapors. Multiconductor or optical multifiber cables in conduit shall be sealed as described in 505.16(B)(4).Exception No. 1: Cables passing from an enclosure or room that is unclassified as a result of Type Z pressurization into a Zone 2 location shall not require a seal at the boundary.Exception No. 2: Shielded cables and twisted pair cables shall not require removal of the shielding material or separation of the twisted pairs if the termination is by an approved means to minimize the entrance of gases or vapors and prevent propagation of flame into the cable core.Restricted Breathing Enclosures "nR". Cables entering restricted breathing enclosures required to be restricted breathing shall be sealed at the point of entrance into the enclosure. These seals shall be installed in accordance with 505.16(D). Multiconductor cables or multifiber optical fiber cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall be sealed in the Zone 2 location. The jacket and any other coverings shall be removed to allow the sealing compound to surround each individual insulated conductor or optical fiber tube to minimize the passage of gases and vapors. Multiconductor cables or optical fiber cables in conduit shall be sealed as described in 505.16(C)(1)(b).Exception No. 1: Cables passing from an enclosure or room that is unclassified as a result of Type Z pressurization into a Zone 2 location shall not require a seal at the boundary.Exception No. 2: Shielded cables and twisted pair cables terminated with fittings listed for the location shall not require removal of the shielding material or separation of the twisted pairs.Cables That Will Not Transmit Gases or Vapors. Cables with a gas/vaportight continuous sheath that will not transmit gases or vapors through the cable core in excess of the quantity permitted for seal fittings shall not be required to be sealed except as required in 505.16(C)(2)(b). The minimum length of such cable run shall not be less than the length that limits gas or vapor flow through the cable core to the rate permitted for seal fittings [200 cm3/hr (0.007 ft3/hr) of air at a pressure of 1500 pascals (6 in. of water)].Informational Note No. 1: See ANSI/UL 2225, Cables and Cable-Fittings for Use in Hazardous (Classified) Locations, for further information on construction, testing, and marking of cables, cable fittings, and cord connectors.Informational Note No. 2: The cable core does not include the interstices of the conductor strands.Cables Capable of Transmitting Gases or Vapors. Cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall not be required to be sealed except as required in 505.16(C)(2)(b), unless the cable is attached to process equipment or devices that might cause a pressure in excess of 1500 pascals (6 in. of water) to be exerted at a cable end, in which case a seal, barrier, or other means shall be provided to prevent migration of flammables into an unclassified area.Exception: Cables with an unbroken gas/vaportight continuous sheath shall be permitted to pass through a Zone 2 location without seals.Cables Without a Gas/Vaportight Continuous Sheath. Cables that do not have a gas/vaportight continuous sheath shall be sealed at the boundary of the Zone 2 and unclassified location to minimize the passage of gases or vapors into an unclassified location.Informational Note: The cable sheath can be either metal or a nonmetallic material. [505.16(C)(2)](https://2023.antflix.net#505.16(C)(2)) | https://2023.antflix.net#505.16(C)(2) |
Chaptewr 5 Special Occupancies | 505.16(D) | Where required, seals in Zones 0, 1, and 2 locations shall comply with 505.16(D)(1) through (D)(5). [505.16(D)](https://2023.antflix.net#505.16(D)) | https://2023.antflix.net#505.16(D) |
Chaptewr 5 Special Occupancies | 505.16(D)(1) | Enclosures for connections or equipment shall be provided with an integral means for sealing, or sealing fittings listed for the location shall be used. Sealing fittings shall be listed for use with one or more specific compounds and shall be accessible. [505.16(D)(1)](https://2023.antflix.net#505.16(D)(1)) | https://2023.antflix.net#505.16(D)(1) |
Chaptewr 5 Special Occupancies | 505.16(D)(2) | The compound shall provide a seal against passage of gas or vapors through the seal fitting, shall not be affected by the surrounding atmosphere or liquids, and shall not have a melting point less than 93°C (200°F). [505.16(D)(2)](https://2023.antflix.net#505.16(D)(2)) | https://2023.antflix.net#505.16(D)(2) |
Chaptewr 5 Special Occupancies | 505.16(D)(3) | In a completed seal, the minimum thickness of the sealing compound shall not be less than the trade size of the sealing fitting and, in no case, less than 16 mm (5/8 in.). Exception: Listed cable sealing fittings shall not be required to have a minimum thickness equal to the trade size of the fitting. [505.16(D)(3)](https://2023.antflix.net#505.16(D)(3)) | https://2023.antflix.net#505.16(D)(3) |
Chaptewr 5 Special Occupancies | 505.16(D)(4) | Splices and taps shall not be made in fittings intended only for sealing with compound, nor shall other fittings in which splices or taps are made be filled with compound. [505.16(D)(4)](https://2023.antflix.net#505.16(D)(4)) | https://2023.antflix.net#505.16(D)(4) |
Chaptewr 5 Special Occupancies | 505.16(D)(5) | The cross-sectional area of the conductors or optical fiber tubes (metallic or nonmetallic) permitted in a seal shall not exceed 25 percent of the cross-sectional area of a rigid metal conduit of the same trade size unless it is specifically listed for a higher percentage of fill. [505.16(D)(5)](https://2023.antflix.net#505.16(D)(5)) | https://2023.antflix.net#505.16(D)(5) |
Chaptewr 5 Special Occupancies | 505.16(E)(1) | Where there is a probability that liquid or other condensed vapor may be trapped within enclosures for control equipment or at any point in the raceway system, approved means shall be provided to prevent accumulation or to permit periodic draining of such liquid or condensed vapor. [505.16(E)(1)](https://2023.antflix.net#505.16(E)(1)) | https://2023.antflix.net#505.16(E)(1) |
Chaptewr 5 Special Occupancies | 505.16(E)(2) | Where liquid or condensed vapor may accumulate within motors or generators, joints and conduit systems shall be arranged to minimize entrance of liquid. If means to prevent accumulation or to permit periodic draining are necessary, such means shall be provided at the time of manufacture and shall be considered an integral part of the machine. [505.16(E)(2)](https://2023.antflix.net#505.16(E)(2)) | https://2023.antflix.net#505.16(E)(2) |
Chaptewr 5 Special Occupancies | 505.17(A) | A flexible cord shall be permitted for connection between portable lighting equipment or other portable utilization equipment and the fixed portion of their supply circuit. Flexible cord shall also be permitted in restricted industrial establishments for any segment of the circuit where installation of one of the fixed wiring methods of 505.15(B) and (C) will not provide the flexibility needed to minimize the transmission of vibration from equipment during operation or to allow for movement after installation during maintenance operations. The flexible cord shall be protected against physical damage and be continuous for the entire length of the cord from equipment connection to equipment connection. Where flexible cords are used, the cords shall comply with the following: Be of a type listed for extra-hard usageContain, in addition to the conductors of the circuit, an equipment grounding conductor complying with 400.23Be connected to terminals or to supply conductors in an approved mannerBe supported by clamps or by other suitable means in such a manner that there will be no tension on the terminal connectionsWhere the flexible cord enters boxes, fittings, or enclosures that are required to be explosionproof or flameproof, be terminated with a listed cord connector that maintains the type of protectionWhere entering an increased safety "e" enclosure, be terminated with a listed increased safety "e" cord connectorInformational Note No. 1: See 400.10 for permitted uses of flexible cords.Informational Note No. 2: See Article 100 for the definition of restricted industrial establishment [as applied to hazardous (classified) locations].Electric submersible pumps with means for removal without entering the wet-pit shall be considered portable utilization equipment. The extension of the flexible cord within a suitable raceway between the wet-pit and the power source shall be permitted.Electric mixers intended for travel into and out of open-type mixing tanks or vats shall be considered portable utilization equipment.Informational Note No. 3: See 505.18 for flexible cords exposed to liquids having a deleterious effect on the conductor insulation. [505.17(A)](https://2023.antflix.net#505.17(A)) | https://2023.antflix.net#505.17(A) |
Chaptewr 5 Special Occupancies | 505.17(B) | To facilitate replacements, process control instruments shall be permitted to be connected through flexible cords, attachment plugs, and receptacles, provided that all of the following conditions apply: A switch listed for Zone 2 is provided so that the attachment plug is not depended on to interrupt current, unless the circuit is type "ia," "ib," or "ic" protection, in which case the switch is not required.The current does not exceed 3 amperes at 120 volts, nominal.The power-supply cord does not exceed 900 mm (3 ft), is of a type listed for extra-hard usage or for hard usage if protected by location, and is supplied through an attachment plug and receptacle of the locking and grounding type.Only necessary receptacles are provided.The receptacle carries a label warning against unplugging under load. [505.17(B)](https://2023.antflix.net#505.17(B)) | https://2023.antflix.net#505.17(B) |
Chaptewr 5 Special Occupancies | 505.18(A) | For type of protection "e," field wiring conductors shall be copper. Every conductor (including spares) that enters Type "e" equipment shall be terminated at a Type "e" terminal. [505.18(A)](https://2023.antflix.net#505.18(A)) | https://2023.antflix.net#505.18(A) |
Chaptewr 5 Special Occupancies | 505.18(B) | Where condensed vapors or liquids may collect on, or come in contact with, the insulation on conductors, such insulation shall be of a type identified for use under such conditions, or the insulation shall be protected by a sheath of lead or by other approved means. [505.18(B)](https://2023.antflix.net#505.18(B)) | https://2023.antflix.net#505.18(B) |
Chaptewr 5 Special Occupancies | 505.19 | There shall be no uninsulated exposed parts, such as electrical conductors, buses, terminals, or components, that operate at more than 30 volts (15 volts in wet locations). These parts shall additionally be protected by type of protection "ia", "ib", or "ic" that is suitable for the location. [505.19](https://2023.antflix.net#505.19) | https://2023.antflix.net#505.19 |
Chaptewr 5 Special Occupancies | 505.20(A) | In Zone 0 locations, only equipment specifically listed and marked as suitable for the location shall be permitted. Exception: Intrinsically safe apparatus listed for use in Class I, Division 1 locations for the same gas, or as permitted by 505.9(B)(2), and with a suitable temperature class shall be permitted. [505.20(A)](https://2023.antflix.net#505.20(A)) | https://2023.antflix.net#505.20(A) |
Chaptewr 5 Special Occupancies | 505.20(B) | In Zone 1 locations, only equipment specifically listed and marked as suitable for the location shall be permitted. Exception No. 1: Equipment identified for use in Class I, Division 1 or listed for use in Zone 0 locations for the same gas, or as permitted by 505.9(B)(2), and with a suitable temperature class shall be permitted. Exception No. 2: Equipment identified for Zone 1 or Zone 2 type of protection "p" shall be permitted. [505.20(B)](https://2023.antflix.net#505.20(B)) | https://2023.antflix.net#505.20(B) |
Chaptewr 5 Special Occupancies | 505.20(C) | In Zone 2 locations, only equipment specifically listed and marked as suitable for the location shall be permitted. Exception No. 1: Equipment listed for use in Zone 0 or Zone 1 locations for the same gas, or as permitted by 505.9(B)(2), and with a suitable temperature class shall be permitted. Exception No. 2: Equipment identified for Zone 1 or Zone 2 type of protection "p" shall be permitted. Exception No. 3: Equipment identified for use in Class I, Division 1 or Division 2 locations for the same gas, or as permitted by 505.9(B)(2), and with a suitable temperature class shall be permitted. Exception No. 4: In Zone 2 locations, the installation of open or nonexplosionproof or nonflameproof enclosed motors such as squirrel-cage induction motors without brushes, switching mechanisms, or similar arc-producing devices that are not identified for use in a Zone 2 location shall be permitted. Exception No. 5: The exposed surface of space heaters used to reduce condensation of moisture during shutdown periods shall not exceed 80 percent of the autoignition temperature in degrees Celsius of the gas or vapor involved when operated at rated voltage, and the maximum space heater surface temperature [based on a 40°C or higher marked ambient] shall be permanently marked on a visible nameplate mounted on the motor. Otherwise, space heaters shall be identified for Class I, Division 2 or Zone 2 locations. Exception No. 6: A sliding contact shaft bonding device used for the purpose of maintaining the rotor at ground potential shall be permitted where the potential discharge energy is determined to be nonincendive for the application. The shaft bonding device shall be permitted to be installed on the inside or the outside of the motor. Informational Note No. 1: It is important to consider the temperature of internal and external surfaces that might be exposed to the flammable atmosphere. Informational Note No. 2: It is important to consider the risk of ignition due to currents arcing across discontinuities and overheating of parts in multi-section enclosures of large motors and generators. Such motors and generators might need equipotential bonding jumpers across joints in the enclosure and from enclosure to ground. Where the presence of ignitible gases or vapors is suspected, clean air purging might be needed immediately prior to and during start-up periods. Informational Note No. 3: See IEEE STD 1349, IEEE Guide for the Application of Electric Machines in Zone 2 and Class I, Division 2 Hazardous (Classified) Locations, for information on the application of rotating electric machines including shaft bonding devices and potential discharge energy calculations. [505.20(C)](https://2023.antflix.net#505.20(C)) | https://2023.antflix.net#505.20(C) |
Chaptewr 5 Special Occupancies | 505.20(D) | Equipment marked Group IIC shall be permitted for applications requiring Group IIA or Group IIB equipment. Similarly, equipment marked Group IIB shall be permitted for applications requiring Group IIA equipment. Equipment marked for a specific gas or vapor shall be permitted for applications where the specific gas or vapor may be encountered. Informational Note: One common example combines these markings with equipment marked IIB +H2. This equipment is suitable for applications requiring Group IIA equipment, Group IIB equipment, or equipment for hydrogen atmospheres. [505.20(D)](https://2023.antflix.net#505.20(D)) | https://2023.antflix.net#505.20(D) |
Chaptewr 5 Special Occupancies | 505.20(E) | Electrical equipment installed in hazardous (classified) locations shall be installed in accordance with the instructions (if any) provided by the manufacturer. [505.20(E)](https://2023.antflix.net#505.20(E)) | https://2023.antflix.net#505.20(E) |
Chaptewr 5 Special Occupancies | 505.22 | In Zone 1 locations, increased safety "e" motors and generators of all voltage ratings shall be listed for Zone 1 locations, and shall comply with all of the following: Motors shall be marked with the current ratio, IA/IN, and time, tE.Motors shall have controllers marked with the model or identification number, output rating (horsepower or kilowatt), full-load amperes, starting current ratio (IA/IN), and time (tE) of the motors that they are intended to protect; the controller marking shall also include the specific overload protection type (and setting, if applicable) that is listed with the motor or generator.Connections shall be made with the specific terminals listed with the motor or generator.Terminal housings shall be permitted to be of substantial, nonmetallic, nonburning material, provided an internal grounding means between the motor frame and the equipment grounding connection is incorporated within the housing.The provisions of Part III of Article 430 shall apply regardless of the voltage rating of the motor.The motors shall be protected against overload by a separate overload device that is responsive to motor current. This device shall be selected to trip or shall be rated in accordance with the listing of the motor and its overload protection.Sections 430.32(C) and 430.44 shall not apply to such motors.The motor overload protection shall not be shunted or cut out during the starting period.Informational Note: See ANSI/UL 122001, General Requirements for Electrical Ignition Systems for Internal Combustion Engines in Class I, Division 2 or Zone 2, Hazardous (Classified) Locations, for information on ignition systems for reciprocating engines installed in Zone 2 hazardous (classified) locations. Reciprocating engine—driven generators, compressors, and other equipment installed in Zone 2 locations might present a risk of ignition of flammable materials associated with fuel, starting, and compression due to inadvertent release or equipment malfunction by the engine ignition system and controls. [505.22](https://2023.antflix.net#505.22) | https://2023.antflix.net#505.22 |
Chaptewr 5 Special Occupancies | 505.26 | Process-connected equipment including, but not limited to, canned pumps, submersible pumps, and flow, pressure, temperature, or analysis measurement instruments shall be sealed with a process seal to prevent the migration of process fluids from the designed containment into the external electrical system. Process-connected electrical equipment that incorporates a single process seal, such as a single compression seal, diaphragm, or tube to prevent flammable or combustible fluids from entering a conduit or cable system capable of transmitting fluids, shall be provided with an additional means to mitigate a single process seal failure. The additional means might include, but is not limited to, the following: A suitable barrier meeting the process temperature and pressure conditions to which the barrier is subjected upon failure of the single process seal. There shall be a vent or drain between the single process seal and the suitable barrier. Indication of the single process seal failure shall be provided by visible leakage, an audible whistle, or other means of monitoring.A listed Type MI cable assembly, rated at not less than 125 percent of the process pressure and not less than 125 percent of the maximum process temperature (in degrees Celsius), installed between the cable or conduit and the single process seal.A drain or vent located between the single process seal and a conduit or cable seal. The drain or vent shall be sufficiently sized to prevent overpressuring the conduit or cable seal above 6 in. water column (1493 Pa). Indication of the single process seal failure shall be provided by visible leakage, an audible whistle, or other means of monitoring.An add-on secondary seal marked "secondary seal" and rated for the pressure and temperature conditions to which it will be subjected upon failure of the single process seal.Process-connected electrical equipment that does not rely on a single process seal or is listed and marked "single seal", "dual seal", or "dual seal without annunciation" shall not be required to be provided with an additional means of sealing.Process-connected electrical equipment marked "single seal - install conduit or cable seal" shall be sealed in accordance with 505.16.Informational Note: See ANSI/UL 122701, Requirements for Process Sealing Between Electrical Systems and Flammable or Combustible Process Fluids, for construction and testing requirements for process sealing of listed and marked single seal, dual seal, or secondary seal equipment. [505.26](https://2023.antflix.net#505.26) | https://2023.antflix.net#505.26 |
Chaptewr 5 Special Occupancies | 505.30 | Regardless of the voltage of the electrical system, wiring systems and equipment shall comply with 505.30(A) and (B). [505.30](https://2023.antflix.net#505.30) | https://2023.antflix.net#505.30 |
Chaptewr 5 Special Occupancies | 505.30(A) | Wiring systems and equipment shall be grounded in accordance with Part I and Part VI of Article 250, as applicable. [505.30(A)](https://2023.antflix.net#505.30(A)) | https://2023.antflix.net#505.30(A) |
Chaptewr 5 Special Occupancies | 505.30(B) | Wiring systems and equipment shall be bonded in accordance with Part I and Part V of Article 250, as applicable, and 505.30(B)(1) and (B)(2). [505.30(B)](https://2023.antflix.net#505.30(B)) | https://2023.antflix.net#505.30(B) |
Chaptewr 5 Special Occupancies | 505.30(B)(1) | Bonding shall comply with 505.30(B)(1)(a) and (B)(1)(b). The locknut-bushing and double-locknut types of contacts shall not be depended on for bonding purposes, but bonding jumpers with identified fittings or other approved means of bonding shall be used. These bonding means shall apply to all metal raceways, fittings, boxes, cable trays, and enclosures, and other parts of raceway systems between hazardous (classified) locations and the point of grounding for service equipment or point of grounding for a separately derived system. Metal struts, angles, or channels provided for support and mechanical or physical protection as permitted in 335.4(5), 336.10(7)(c), or 722.135(C) shall be bonded in accordance with 250.102.Where the branch-circuit overcurrent protection is located on the load side of the disconnecting means, the specific bonding means shall be permitted to end at the nearest point where the grounded circuit conductor and the grounding electrode conductor are connected together on the line side of the building or structure disconnecting means as specified in 250.32(B). [505.30(B)(1)](https://2023.antflix.net#505.30(B)(1)) | https://2023.antflix.net#505.30(B)(1) |
Chaptewr 5 Special Occupancies | 505.30(B)(2) | Flexible metal conduit and liquidtight flexible metal conduit shall comply with 505.30(B)(2)(a) and (B)(2)(b). Flexible metal conduit and liquidtight flexible metal conduit shall include an equipment bonding jumper of the wire type in accordance with 250.102.In Zone 2 locations, the bonding jumper shall not be required where all of the following conditions are met:Listed liquidtight flexible metal conduit 1.8 m (6 ft) or less in length, with fittings listed for grounding, is used.Overcurrent protection in the circuit is limited to 10 amperes or less.The load is part of a meter, instrument, or relay circuit. [505.30(B)(2)](https://2023.antflix.net#505.30(B)(2)) | https://2023.antflix.net#505.30(B)(2) |
Chaptewr 5 Special Occupancies | 506.1(A) | This article covers the requirements for the zone classification system for electrical and electronic equipment and wiring for all voltages where fire and explosion hazards might exist due to combustible dusts, combustible fibers/flyings, or ignitible fibers/flyings for the following: Zone 20 hazardous (classified) locationsZone 21 hazardous (classified) locationsZone 22 hazardous (classified) locationsInformational Note No. 1: See 505.20 or 505.22 for Zone 0, Zone 1, or Zone 2 hazardous (classified) locations where fire or explosion hazards might exist due to flammable gases, flammable vapors, or flammable liquids.Informational Note No. 2: Zone 20, Zone 21, and Zone 22 area classifications are based on the modified IEC area classification system as defined in ANSI/ISA 60079-10-2 (12.10.05), Explosive Atmospheres - Part 10-2: Classification of Areas - Combustible Dust Atmospheres.Informational Note No. 3: See NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, for information regarding classification of hazardous (classified) locations using Zone methodology. [506.1(A)](https://2023.antflix.net#506.1(A)) | https://2023.antflix.net#506.1(A) |
Chaptewr 5 Special Occupancies | 506.1(B) | This article does not cover electrical and electronic equipment and wiring of all voltages in the following: Class I, Class II, or Class III, Division 1 or Division 2 hazardous (classified) locations.Zone 0, Zone 1, or Zone 2 hazardous (classified) locations.Locations subject to the unique risk and explosion hazards associated with explosives, pyrotechnics, or blasting agents.Locations where pyrophoric materials are the only materials used or handled.Features of equipment that involve nonelectrical potential sources of ignition (e.g., couplings, pumps, gearboxes, brakes, hydraulic and pneumatic motors, fan, engine, compressor).Informational Note No. 1: Common nonelectrical potential sources of ignition include hot surfaces and mechanically generated sparks.Informational Note No. 2: See ANSI/UL 80079-36, Explosive Atmospheres - Part 36: Non-Electrical Equipment for Explosive Atmospheres - Basic Method and Requirements, and ANSI/UL 80079-37, Explosive Atmospheres - Part 37: Non-Electrical Equipment for Explosive Atmospheres - Non-Electrical Type of Protection Constructional Safety "c" Control of Ignition Source "b", Liquid Immersion "k", for additional information. [506.1(B)](https://2023.antflix.net#506.1(B)) | https://2023.antflix.net#506.1(B) |
Chaptewr 5 Special Occupancies | 506.4 | Areas designated as hazardous (classified) or unclassified locations shall be documented on an area classification drawing and other associated documentation. This documentation shall be made available to the AHJ and to those authorized to design, install, inspect, maintain, or operate electrical equipment. Informational Note No. 1: See ANSI/UL 60079-28, Explosive Atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation, for information concerning the installation of equipment using optical emissions technology (such as laser equipment) that could potentially become an ignition source in hazardous (classified) locations. Informational Note No. 2: See IEC/IEEE 60079-30-2, Explosive atmospheres - Part 30-2: Electrical Resistance Trace Heating - Application Guide for Design, Installation and Maintenance, for information on electrical resistance trace heating for hazardous (classified) locations. Informational Note No. 3: See IEEE 844.2/CSA C293.2, IEEE/CSA Standard for Skin Effect Trace Heating of Pipelines, Vessels, Equipment, and Structures - Application Guide for Design, Installation, Testing, Commissioning, and Maintenance, for information on electric skin effect trace heating for hazardous (classified) locations. Informational Note No. 4: See IEEE 844.4/CSA C293.4, IEEE/CSA Standard for Impedance Heating of Pipelines and Equipment - Application Guide for Design, Installation, Testing, Commissioning, and Maintenance, for information on electric impedance heating for hazardous (classified) locations. [506.4](https://2023.antflix.net#506.4) | https://2023.antflix.net#506.4 |
Chaptewr 5 Special Occupancies | 506.5(A) | Locations shall be classified on the basis of the properties of the combustible dust, combustible fibers/flyings, or ignitible fibers/flyings that might be present, and the likelihood that a combustible or ignitible concentration or quantity is present. Each room, section, or area shall be considered individually in determining its classification. [506.5(A)](https://2023.antflix.net#506.5(A)) | https://2023.antflix.net#506.5(A) |
Chaptewr 5 Special Occupancies | 506.5(B) | Zone 20, Zone 21, and Zone 22 locations are those in which combustible dust, combustible fibers/flyings, or ignitible fibers/flyings are or might be present in the air or in layers, in quantities sufficient to produce explosible or ignitible mixtures. Zone 20, Zone 21, and Zone 22 locations shall include those specified in 506.5(B)(1), (B)(2), and (B)(3). Informational Note: Through the exercise of ingenuity in the layout of electrical installations for hazardous (classified) locations, it is frequently possible to locate much of the equipment in a reduced level of classification to reduce the amount of special equipment required. [506.5(B)](https://2023.antflix.net#506.5(B)) | https://2023.antflix.net#506.5(B) |
Chaptewr 5 Special Occupancies | 506.5(B)(1) | A Zone 20 location is a location where one of the following apply: Ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings are present continuously or for long periods of time.Group IIIC combustible dusts are present in hazardous quantities continuously or for long periods of time. [506.5(B)(1)](https://2023.antflix.net#506.5(B)(1)) | https://2023.antflix.net#506.5(B)(1) |
Chaptewr 5 Special Occupancies | 506.5(B)(2) | A Zone 21 location is a location where one of the following apply: Ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings are likely to exist occasionally under normal operating conditions.Ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings might exist frequently because of repair or maintenance operations or because of leakage.Equipment is operated or processes are carried on of such a nature that equipment breakdown or faulty operations could result in the release of ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings and also cause simultaneous failure of electrical equipment in a mode to cause the electrical equipment to become a source of ignition.The location is adjacent to a Zone 20 location from which ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings could be communicated.Exception: When communication from an adjacent Zone 20 location is minimized by adequate positive pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided.Group IIIC combustible dusts are present in hazardous quantities occasionally, under normal or abnormal operating conditions, or frequently because of repair or maintenance operations or because of leakage.Informational Note No. 1: See ANSI/ISA 60079-10-2 (12.10.05), Explosive Atmospheres - Part 10-2: Classification of Areas - Combustible Dust Atmospheres, regarding the classification of Zone 21 locations.Informational Note No. 2: This classification usually includes the following:Locations outside dust containment and in the immediate vicinity of access doors subject to frequent removal or opening for operation purposes when internal combustible mixtures are presentLocations outside dust containment in the proximity of filling and emptying points, feed belts, sampling points, truck dump stations, belt dump over points, and so on, where no measures are employed to prevent the formation of combustible mixturesLocations outside dust containment where dust accumulates and where, due to process operations, the dust layer is likely to be disturbed and form combustible mixturesLocations inside dust containment where explosible dust clouds are likely to occur (but neither continuously, nor for long periods, nor frequently), for example, silos (if filled and/or emptied only occasionally) and the dirty side of filters if large self-cleaning intervals are occurring [506.5(B)(2)](https://2023.antflix.net#506.5(B)(2)) | https://2023.antflix.net#506.5(B)(2) |
Chaptewr 5 Special Occupancies | 506.5(B)(3) | A Zone 22 location is a location where one of the following apply: Ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings are not likely to occur in normal operation and, if they do occur, will only persist for a short period.Combustible dust, combustible fibers/flyings, or ignitible fibers/flyings are handled, processed, or used, but the dust or fibers/flyings are normally confined within closed containers of closed systems from which they can escape only as a result of the abnormal operation of the equipment with which the dust or fibers/flyings are handled, processed, or used.The location is adjacent to a Zone 21 location, from which ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings could be communicated.Exception No. 1: When communication from an adjacent Zone 21 location is minimized by adequate positive pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided.Exception No. 2: For Group IIIC combustible dusts or metal combustible fibers/flyings, there shall only be Zone 20 or 21 locations.Informational Note No. 1: See ANSI/ISA 60079-10-2 (12.10.05), Explosive Atmospheres - Part 10-2: Classification of Areas - Combustible Dust Atmospheres, regarding the classification of Zone 22 locations.Informational Note No. 2: Zone 22 locations usually include the following:Outlets from bag filter vents (in the event of a malfunction, there can be emission of combustible mixtures)Locations near equipment that has to be opened at infrequent intervals or equipment that from experience can easily form leaks where, due to pressure above atmospheric, dust will blow outPneumatic equipment or flexible connections that can become damagedStorage locations for bags containing dusty product (failure of bags can occur during handling, causing dust leakage)Locations where controllable dust layers are formed that are likely to be raised into explosible dust-air mixturesOnly if the layer is removed by cleaning before hazardous dust-air mixtures can be formed is the area designated unclassified.Informational Note No. 3: Protective measures to reduce the formation of explosible dust-air mixtures can often result in a Zone 21 location being classified as a Zone 22 location, or possibly unclassified. Such measures include local exhaust ventilation. [506.5(B)(3)](https://2023.antflix.net#506.5(B)(3)) | https://2023.antflix.net#506.5(B)(3) |
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