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Chaptewr 5 Special Occupancies | 500.7(D) | This protection technique shall be permitted for equipment in any hazardous (classified) location for which it is identified. [500.7(D)](https://2023.antflix.net#500.7(D)) | https://2023.antflix.net#500.7(D) |
Chaptewr 5 Special Occupancies | 500.7(E) | This protection technique shall be permitted for equipment in Class I, Division 1 or Division 2; Class II, Division 1 or Division 2; or Class III, Division 1 or Division 2 locations. [500.7(E)](https://2023.antflix.net#500.7(E)) | https://2023.antflix.net#500.7(E) |
Chaptewr 5 Special Occupancies | 500.7(F) | This protection technique shall be permitted for equipment in Class I, Division 2; Class II, Division 2; or Class III, Division 1 or 2 locations. [500.7(F)](https://2023.antflix.net#500.7(F)) | https://2023.antflix.net#500.7(F) |
Chaptewr 5 Special Occupancies | 500.7(G) | This protection technique shall be permitted for equipment in Class I. Division 2; Class II, Division 2; or Class III, Division 1 or 2 locations. [500.7(G)](https://2023.antflix.net#500.7(G)) | https://2023.antflix.net#500.7(G) |
Chaptewr 5 Special Occupancies | 500.7(H) | This protection technique shall be permitted for equipment in Class I, Division 2; Class II, Division 2; or Class III, Division 1 or 2 locations. [500.7(H)](https://2023.antflix.net#500.7(H)) | https://2023.antflix.net#500.7(H) |
Chaptewr 5 Special Occupancies | 500.7(I) | This protection technique shall be permitted for current-interrupting contacts in Class I, Division 2 locations as described in 501.115(B)(1)(2). [500.7(I)](https://2023.antflix.net#500.7(I)) | https://2023.antflix.net#500.7(I) |
Chaptewr 5 Special Occupancies | 500.7(J) | This protection technique shall be permitted for equipment in Class I, Division 2; Class II, Division 2; or Class III, Division 1 or 2 locations. [500.7(J)](https://2023.antflix.net#500.7(J)) | https://2023.antflix.net#500.7(J) |
Chaptewr 5 Special Occupancies | 500.7(K) | A detection system for flammable gases shall be permitted as a means of protection in restricted industrial establishments. [500.7(K)](https://2023.antflix.net#500.7(K)) | https://2023.antflix.net#500.7(K) |
Chaptewr 5 Special Occupancies | 500.7(K)(1) | Any gas detection system used as a protection technique shall meet all of the requirements in 500.7(K)(1)(a) through (K)(1)(e). The gas detection equipment used shall be listed for Class I, Division 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 and its listing, installation location(s), alarm and shutdown criteria, and 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 500.7(K)(2), (K)(3), or (K)(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 500, Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 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. [500.7(K)(1)](https://2023.antflix.net#500.7(K)(1)) | https://2023.antflix.net#500.7(K)(1) |
Chaptewr 5 Special Occupancies | 500.7(K)(2) | A location, enclosed space, or building that is classified as a Class I, Division 1 location due to inadequate ventilation and is provided with a detection system for flammable gases shall be permitted to use electrical equipment, installation methods, and wiring practices suitable for Class I, Division 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). [500.7(K)(2)](https://2023.antflix.net#500.7(K)(2)) | https://2023.antflix.net#500.7(K)(2) |
Chaptewr 5 Special Occupancies | 500.7(K)(3) | Any building or enclosed space that does not contain a source of flammable gases or vapors that is located in, or has an opening into, a Class I, Division 2 hazardous (classified) location and 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 Class I, Division 2.The power disconnecting device(s) shall be suitable for Class I, Division 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. [500.7(K)(3)](https://2023.antflix.net#500.7(K)(3)) | https://2023.antflix.net#500.7(K)(3) |
Chaptewr 5 Special Occupancies | 500.7(K)(4) | Inside the interior of a control panel containing instrumentation or other equipment using or measuring flammable liquids, gases, or vapors which is provided with a detection system for flammable gases shall be permitted to use electrical equipment, installation methods, and wiring practices suitable for Class I, Division 2 installations. An alarm (audible or visual, or both) shall be sounded at not more than 40 percent of the lower flammable limit. [500.7(K)(4)](https://2023.antflix.net#500.7(K)(4)) | https://2023.antflix.net#500.7(K)(4) |
Chaptewr 5 Special Occupancies | 500.7(L) | This protection technique shall be permitted for equipment in Class I or II, Division 1 or 2 locations for which the equipment is identified. Informational Note: The identified class and division depends on the intended explosive atmosphere and the number of faults applied as part of the protection technique evaluation. [500.7(L)](https://2023.antflix.net#500.7(L)) | https://2023.antflix.net#500.7(L) |
Chaptewr 5 Special Occupancies | 500.7(M) | This protection technique shall be permitted for equipment in Class I or II, Division 2 locations for which the equipment is identified. Informational Note: The identified class and division depends on the intended explosive atmosphere as part of the protection technique evaluation. [500.7(M)](https://2023.antflix.net#500.7(M)) | https://2023.antflix.net#500.7(M) |
Chaptewr 5 Special Occupancies | 500.7(N) | This protection technique shall be permitted for equipment in Class I or II, Division 1 or 2 locations for which the equipment is identified. Informational Note: The identified class and division depends on the intended explosive atmosphere and the number of faults applied as part of the protection technique evaluation. [500.7(N)](https://2023.antflix.net#500.7(N)) | https://2023.antflix.net#500.7(N) |
Chaptewr 5 Special Occupancies | 500.7(O) | This protection technique shall be permitted for skin effect trace heating equipment in Class I, Division 2; Class II, Division 2; or Class III, Division 2 locations for which it is listed. [500.7(O)](https://2023.antflix.net#500.7(O)) | https://2023.antflix.net#500.7(O) |
Chaptewr 5 Special Occupancies | 500.7(P) | This protection technique shall be permitted for electrical resistance trace heating equipment in Class I, Division 1; Class I, Division 2; Class II, Division 1; Class II, Division 2; Class III, Division 1; or Class III, Division 2 locations for which it is listed. [500.7(P)](https://2023.antflix.net#500.7(P)) | https://2023.antflix.net#500.7(P) |
Chaptewr 5 Special Occupancies | 500.7(Q) | This protection technique shall be permitted for impedance heating equipment in Class I, Division 2; Class II, Division 2; or Class III, Division 2 locations for which it is listed. [500.7(Q)](https://2023.antflix.net#500.7(Q)) | https://2023.antflix.net#500.7(Q) |
Chaptewr 5 Special Occupancies | 500.7(R) | This protection technique shall be permitted for equipment in Class I, Division 2 locations. [500.7(R)](https://2023.antflix.net#500.7(R)) | https://2023.antflix.net#500.7(R) |
Chaptewr 5 Special Occupancies | 500.7(S) | This protection technique shall be permitted for equipment in Class I, Division 2 locations. [500.7(S)](https://2023.antflix.net#500.7(S)) | https://2023.antflix.net#500.7(S) |
Chaptewr 5 Special Occupancies | 500.7(T) | This protection technique shall be permitted for equipment in Class I, Division 2; Class II, Division 2; Class III, Division 1; or Class III, Division 2 locations. [500.7(T)](https://2023.antflix.net#500.7(T)) | https://2023.antflix.net#500.7(T) |
Chaptewr 5 Special Occupancies | 500.7(U) | Protection techniques not specified in 500.7(A) through (T) shall be permitted for use in equipment listed for use in hazardous (classified) locations. Informational Note: See ANSI/UL 60079-33, Explosive Atmospheres - Part 33: Equipment Protection by Special Protection "s", for additional information. [500.7(U)](https://2023.antflix.net#500.7(U)) | https://2023.antflix.net#500.7(U) |
Chaptewr 5 Special Occupancies | 500.8 | Explosionproof or dust-ignitionproof equipment shall not be permitted for use at temperatures lower than -25°C (-13°F) unless they are identified for low-temperature service. Informational Note: At low ambient temperatures, flammable concentrations of vapors might not exist in a location classified as Class I, Division 1 at normal ambient temperature. [500.8](https://2023.antflix.net#500.8) | https://2023.antflix.net#500.8 |
Chaptewr 5 Special Occupancies | 500.8(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 might include certificates demonstrating compliance with applicable equipment standards, indicating special conditions of use, and providing other pertinent information. [500.8(A)](https://2023.antflix.net#500.8(A)) | https://2023.antflix.net#500.8(A) |
Chaptewr 5 Special Occupancies | 500.8(B)(1) | Equipment shall be identified not only for the class of location but also for the explosive, combustible, or ignitible properties of the specific gas, vapor, dust, or fibers/flyings that will be present. In addition, Class I equipment shall not have any exposed surface that operates at a temperature in excess of the autoignition temperature of the specific gas or vapor. Class II equipment shall not have an external temperature higher than that specified in 500.8(D) (2). Class III equipment shall not exceed the maximum surface temperatures specified in 503.5. Exception No. 1: Group D equipment shall be permitted to be used for atmospheres containing butadiene if all conduit runs into explosion-proof equipment are provided with explosionproof seals installed within 450 mm (18 in.) of the enclosure. Exception No. 2: Group C equipment shall be permitted to be used for atmospheres containing allyl glycidyl ether, n-butyl glycidyl ether, ethylene oxide, propylene oxide, and acrolein if all conduit runs into explosionproof equipment are provided with explosionproof seals installed within 450 mm (18 in.) of the enclosure. Informational Note: See 500.8(C)(6)(a) regarding general-purpose equipment. Luminaires and other heat-producing apparatus, switches, circuit breakers, and plugs and receptacles are potential sources of ignition and are investigated for suitability in classified locations. Such types of equipment, as well as cable terminations for entry into explosionproof enclosures, are available as listed for Class I, Division 2 locations. Fixed wiring, however, might use wiring methods that are not evaluated with respect to classified locations. Therefore, wiring products such as cable, raceways, boxes, and fittings are not marked as being suitable for Class I, Division 2 locations. [500.8(B)(1)](https://2023.antflix.net#500.8(B)(1)) | https://2023.antflix.net#500.8(B)(1) |
Chaptewr 5 Special Occupancies | 500.8(B)(2) | Equipment identified for a Division 1 location shall be permitted in a Division 2 location of the same class, group, and temperature class and shall comply with the requirements of 500.8(B)(2)(a) or (B)(2)(b) as applicable. Intrinsically safe apparatus having a control drawing requiring the installation of associated apparatus for a Division 1 installation shall be permitted to be installed in a Division 2 location if the same associated apparatus is used for the Division 2 installation.Equipment required to be explosionproof shall incorporate seals in accordance with 501.15(A) or (D) when the wiring methods of 501.10(B) are employed. [500.8(B)(2)](https://2023.antflix.net#500.8(B)(2)) | https://2023.antflix.net#500.8(B)(2) |
Chaptewr 5 Special Occupancies | 500.8(B)(3) | Where specifically permitted in Part III of Articles 501, 502, and 503, general-purpose equipment or equipment in general-purpose enclosures shall be permitted to be installed in Division 2 locations if the equipment does not constitute a source of ignition under normal operating conditions. [500.8(B)(3)](https://2023.antflix.net#500.8(B)(3)) | https://2023.antflix.net#500.8(B)(3) |
Chaptewr 5 Special Occupancies | 500.8(B)(4) | Equipment that depends on a single compression seal, diaphragm, or tube to prevent flammable or combustible fluids from entering the equipment shall be identified for a Class I, Division 2 location even if installed in an unclassified location. Equipment installed in a Class I, Division 1 location shall be identified for the Class I, Division 1 location. Informational Note: Equipment used for flow measurement is an example of equipment having a single compression seal, diaphragm, or tube. [500.8(B)(4)](https://2023.antflix.net#500.8(B)(4)) | https://2023.antflix.net#500.8(B)(4) |
Chaptewr 5 Special Occupancies | 500.8(B)(5) | Unless otherwise specified, normal operating conditions for motors shall be assumed to be rated full-load steady conditions. [500.8(B)(5)](https://2023.antflix.net#500.8(B)(5)) | https://2023.antflix.net#500.8(B)(5) |
Chaptewr 5 Special Occupancies | 500.8(B)(6) | Where flammable gases, flammable liquid—produced vapors, or combustible liquid-produced vapors and combustible dusts are or might be present at the same time, the simultaneous presence of the specific materials shall be considered when determining the safe operating temperature of the electrical equipment. [500.8(B)(6)](https://2023.antflix.net#500.8(B)(6)) | https://2023.antflix.net#500.8(B)(6) |
Chaptewr 5 Special Occupancies | 500.8(C) | Equipment shall be marked to show the environment for which it has been evaluated. Unless otherwise specified or allowed in 500.8(C)(6), the marking shall include the information specified in 500.8(C)(1) through (C)(5). [500.8(C)](https://2023.antflix.net#500.8(C)) | https://2023.antflix.net#500.8(C) |
Chaptewr 5 Special Occupancies | 500.8(C)(1) | The marking shall specify the class(es) for which the equipment is suitable. [500.8(C)(1)](https://2023.antflix.net#500.8(C)(1)) | https://2023.antflix.net#500.8(C)(1) |
Chaptewr 5 Special Occupancies | 500.8(C)(2) | The marking shall specify the division if the equipment is suitable for Division 2 only. Equipment suitable for Division 1 shall be permitted to omit the division marking. Informational Note: See 500.8(B)(2). Equipment not marked to indicate a division, or marked "Division 1" or "Div. 1," is suitable for both Division 1 and Division 2 locations. Equipment marked "Division 2" or "Div. 2" is suitable for Division 2 locations only. [500.8(C)(2)](https://2023.antflix.net#500.8(C)(2)) | https://2023.antflix.net#500.8(C)(2) |
Chaptewr 5 Special Occupancies | 500.8(C)(3) | The marking shall specify the applicable material classification group(s) or specific gas, vapor, dust, or fiber/flying in accordance with 500.6. Exception: Fixed luminaires marked for use only in Class I, Division 2 or Class II, Division 2 locations shall not be required to indicate the group. Informational Note: A specific gas, vapor, dust, or fiber/flying is typically identified by the generic name, chemical formula, CAS number, or combination thereof. [500.8(C)(3)](https://2023.antflix.net#500.8(C)(3)) | https://2023.antflix.net#500.8(C)(3) |
Chaptewr 5 Special Occupancies | 500.8(C)(4) | The marking shall specify the temperature class or operating temperature at a 40°C ambient temperature, or at the higher ambient temperature if the equipment is rated and marked for an ambient temperature of greater than 40°C. For equipment installed in a Class II, Division 1 location, the temperature class or operating temperature shall be based on operation of the equipment when blanketed with the maximum amount of dust that can accumulate on the equipment. The temperature class, if provided, shall be indicated using the temperature class (T codes) shown in Table 500.8(C)(4). Equipment for Class I and Class II shall be marked with the maximum safe operating temperature, as determined by simultaneous exposure to the combinations of Class I and Class II conditions. Exception: Equipment of the non-heat-producing type, such as junction boxes, conduit, and fittings, and equipment of the heat-producing type having a maximum temperature not more than 100°C shall not be required to have a marked operating temperature or temperature class. Informational Note: More than one marked temperature class or operating temperature, for gases and vapors, dusts, and different ambient temperatures, may appear. [500.8(C)(4)](https://2023.antflix.net#500.8(C)(4)) | https://2023.antflix.net#500.8(C)(4) |
Chaptewr 5 Special Occupancies | 500.8(C)(5) | Electrical equipment designed for use in the ambient temperature range between —25°C to +40°C shall require no ambient temperature marking. For equipment rated for a temperature range other than —25°C to +40°C, the marking shall specify the special range of ambient temperatures in degrees Celsius. The marking shall include either the symbol "Ta" or "Tamb." Informational Note: As an example, such a marking might be "—30°C ≤ Ta ≤ +40°C." [500.8(C)(5)](https://2023.antflix.net#500.8(C)(5)) | https://2023.antflix.net#500.8(C)(5) |
Chaptewr 5 Special Occupancies | 500.8(C)(6) | General-Purpose Equipment. Fixed general-purpose equipment in Class I locations, other than fixed luminaires, that is acceptable for use in Class I, Division 2 locations shall not be required to be marked with the class, division, group, temperature class, or ambient temperature range.Dusttight Equipment, Fixed dusttight equipment, other than fixed luminaires, that is acceptable for use in Class II, Division 2 and Class III locations shall not be required to be marked with the class, division, group, temperature class, or ambient temperature range.Associated Apparatus. Associated intrinsically safe apparatus and associated nonincendive field wiring apparatus that are not protected by an alternative type of protection shall not be marked with the class, division, group, or temperature class. Associated intrinsically safe apparatus and associated nonincendive field wiring apparatus shall be marked with the class, division, and group of the apparatus to which it is to be connected.Simple Apparatus. "Simple apparatus" as defined in Article 100 Part III, shall not be required to be marked with class, division, group, temperature class, or ambient temperature range. [500.8(C)(6)](https://2023.antflix.net#500.8(C)(6)) | https://2023.antflix.net#500.8(C)(6) |
Chaptewr 5 Special Occupancies | 500.8(D)(1) | The temperature marking specified in 500.8(C) shall not exceed the autoignition temperature of the specific gas or vapor to be encountered. Informational Note: See NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, for information on autoignition temperatures of gases and vapors. [500.8(D)(1)](https://2023.antflix.net#500.8(D)(1)) | https://2023.antflix.net#500.8(D)(1) |
Chaptewr 5 Special Occupancies | 500.8(D)(2) | The temperature marking specified in 500.8(C) shall be less than the ignition temperature of the specific dust or metal fiber/flying to be encountered. For organic dusts that might dehydrate or carbonize, the temperature marking shall not exceed the lower of either the ignition temperature or 165°C (329°F). Informational Note: See NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, for minimum ignition temperatures of specific dusts. [500.8(D)(2)](https://2023.antflix.net#500.8(D)(2)) | https://2023.antflix.net#500.8(D)(2) |
Chaptewr 5 Special Occupancies | 500.8(D)(3) | The temperature marking specified in 500.8(C) shall be less than the ignition temperature of the specific fiber/flying to be encountered, except as specified in 500.8(D)(3)(a) or (D)(3)(b). For nonmetal combustible fibers/flyings that might dehydrate or carbonize, the temperature marking shall not exceed the lower of either the ignition temperature or 165°C (329°F).When ignitible fibers/flyings are present, the maximum surface temperatures under operating conditions shall not exceed 165°C (329°F) for equipment that is not subject to overloading, and 120°C (248°F) for equipment (such as motors or power transformers) that might be overloaded. [500.8(D)(3)](https://2023.antflix.net#500.8(D)(3)) | https://2023.antflix.net#500.8(D)(3) |
Chaptewr 5 Special Occupancies | 500.8(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 integrity of the conduit system where applicable. Equipment provided with threaded entries for field wiring connections shall be installed in accordance with 500.8(E)(1) or (E)(2) and with (E)(3). [500.8(E)](https://2023.antflix.net#500.8(E)) | https://2023.antflix.net#500.8(E) |
Chaptewr 5 Special Occupancies | 500.8(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 equipment shall be made up with at least five threads fully engaged. Exception: For listed explosionproof equipment, joints with factory-threaded NPT entries shall be made up with at least four and one-half 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 ASME B1.20.1, Pipe Threads, General Purpose (Inch), and ANSI/UL 1203, Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations, for information on female NPT-threaded entries using modified National Standard Pipe Taper (NPT) threads. [500.8(E)(1)](https://2023.antflix.net#500.8(E)(1)) | https://2023.antflix.net#500.8(E)(1) |
Chaptewr 5 Special Occupancies | 500.8(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 equipment shall have a class of fit of at least 6g/6H and shall 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. [500.8(E)(2)](https://2023.antflix.net#500.8(E)(2)) | https://2023.antflix.net#500.8(E)(2) |
Chaptewr 5 Special Occupancies | 500.8(E)(3) | All unused openings shall be closed with blanking elements or close-up plugs that are listed for the location. The thread engagement shall comply with the requirements of 500.8(E)(1) or (E)(2). [500.8(E)(3)](https://2023.antflix.net#500.8(E)(3)) | https://2023.antflix.net#500.8(E)(3) |
Chaptewr 5 Special Occupancies | 500.8(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 Part II of Articles 501, 502, or 503, as applicable. [500.8(F)](https://2023.antflix.net#500.8(F)) | https://2023.antflix.net#500.8(F) |
Chaptewr 5 Special Occupancies | 500.8(G) | The risk of ignition from optical radiation shall be evaluated for laser equipment, optical fiber equipment, and any other convergent light sources or beams where light is focused in one single point within a hazardous area with a wavelength range of 380 nm to 10 pm. This requirement shall include optical equipment that is located outside the explosive atmosphere, but whose 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 that can be applied to minimize the risk of ignition in explosive atmospheres from optical radiation. Table 500.8(C)(4) Classification of Maximum Surface Temperature Maximum Temperature Temperature Class(T Code) °C °F 450 842 T1 300 572 T2 280 536 T2A 260 500 T2B 230 446 T2C 215 419 T2D 200 392 T3 180 356 T3A 165 329 T3B 160 320 T3C 135 275 T4 120 248 T4A 100 212 T5 85 185 T6 [500.8(G)](https://2023.antflix.net#500.8(G)) | https://2023.antflix.net#500.8(G) |
Chaptewr 5 Special Occupancies | 501.1 | This article covers the requirements for electrical and electronic equipment and wiring for all voltages in Class I, Division 1 and Division 2 locations where flammable gases, flammable liquid—produced vapors, or combustible liquid—produced vapors are or might be present in the air in quantities sufficient to produce explosive or ignitible mixtures. [501.1](https://2023.antflix.net#501.1) | https://2023.antflix.net#501.1 |
Chaptewr 5 Special Occupancies | 501.5 | Equipment listed and marked in accordance with 505.9(C)(2) for use in Zone 0, 1, or 2 locations shall be permitted in Class I, Division 2 locations for the same gas and with a suitable temperature class. Equipment listed and marked in accordance with 505.9(C)(2) for use in Zone 0 locations shall be permitted in Class I, Division 1 or Division 2 locations for the same gas and with a suitable temperature class. [501.5](https://2023.antflix.net#501.5) | https://2023.antflix.net#501.5 |
Chaptewr 5 Special Occupancies | 501.10 | Wiring methods shall comply with 501.10(A) or (B). [501.10](https://2023.antflix.net#501.10) | https://2023.antflix.net#501.10 |
Chaptewr 5 Special Occupancies | 501.10(A)(1) | In Class I, Division 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].Threaded rigid metal conduit (RMC) or threaded intermediate metal conduit (IMC), including RMC or IMC conduit systems with supplemental corrosion protection coatings.PVC conduit, RTRC conduit, or HDPE conduit, 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. The concrete encasement shall be permitted to be omitted where it is in accordance with 514.8(C) or 515.8(A). 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.Type MI cable terminated with fittings listed for the location. Type MI cable shall be installed and supported to avoid tensile stress at the termination fittings.In restricted industrial establishments, Type MC-HL cable listed for use in Class I, Zone 1 or 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, and terminated with fittings listed for the application. If installed in a ladder, ventilated trough, or ventilated channel cable tray, the cable shall be installed in accordance with 392.22. Type MC-HL cable shall be installed in accordance with Part II of Article 330.In restricted industrial establishments, Type ITC-HL cable listed for use in Class I, Division 1 or Zone 1 locations, with a gas/vaportight continuous corrugated metallic sheath and an overall jacket of suitable polymeric material, terminated with fittings listed for the application, and installed in accordance with 335.4.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 501.10(A). These optical fiber cables shall be sealed in accordance with 501.15.In restricted industrial establishments for applications limited to 600 volts nominal or less, and where the cable is not subject to physical damage and is terminated with fittings listed for the location, Type TC-ER-HL cable. If installed in a ladder, ventilated trough, or ventilated channel cable tray, the cable shall be installed in accordance with 392.22. 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. 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, terminated with fittings listed for the location, and installed in accordance with Part II of Article 337. If installed in a ladder, ventilated trough, or ventilated channel cable tray, the cable shall be installed in accordance with 392.22.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. [501.10(A)(1)](https://2023.antflix.net#501.10(A)(1)) | https://2023.antflix.net#501.10(A)(1) |
Chaptewr 5 Special Occupancies | 501.10(A)(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 501.140, 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. The 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 where the cable is 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 fittings.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. [501.10(A)(2)](https://2023.antflix.net#501.10(A)(2)) | https://2023.antflix.net#501.10(A)(2) |
Chaptewr 5 Special Occupancies | 501.10(A)(3) | All boxes and fittings shall be identified for Class I, Division 1. 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, explosionproof cable fittings, and explosionproof cord connectors for entry into enclosures required to be explosionproof. Informational Note No. 2: See ANSI/UL 1203, Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations, for information on construction, testing, and marking of explosionproof conduit fittings for entry into enclosures required to be explosionproof. [501.10(A)(3)](https://2023.antflix.net#501.10(A)(3)) | https://2023.antflix.net#501.10(A)(3) |
Chaptewr 5 Special Occupancies | 501.10(B)(1) | In Class I, Division 2 locations, all wiring methods in accordance with 501.10(A) and 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].Rigid metal conduit (RMC) or intermediate metal conduit (IMC) with listed threaded or threadless fittings, including RMC or IMC conduit systems with supplemental corrosion protection coatings.Enclosed gasketed busways and enclosed gasketed wire-ways.Type PLTC cable or Type PLTC-ER cable used for Class 2 and Class 3 circuits, including installation in cable tray systems. The cable shall be terminated with listed fittings. Type PLTC-ER cable shall include an equipment grounding conductor in addition to a drain wire that might be present.Type ITC cable or Type ITC-ER cable as permitted in 335.4 and terminated with listed fittings. Type ITC-ER cable shall include an equipment grounding conductor in addition to a drain wire.Type MC, Type MV, Type TC, or Type TC-ER cable, including installation in cable tray systems. Type TC-ER cable shall include an equipment grounding conductor in addition to a drain wire that might be present. All cable types shall be terminated with listed fittings.Where metal conduit will not provide the corrosion resistance needed for the installation environment, any of the following shall be permitted:Listed reinforced thermosetting resin conduit (RTRC), factory elbows, and associated fittings, all marked with the suffix -XWPVC-coated RMC, factory elbows, and associated fittingsPVC-coated IMC, factory elbows, and associated fittingsIn restricted industrial establishments, Schedule 80 PVC conduit, factory elbows, and associated fittingsOptical fiber cable 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 501.10(B). Optical fiber cables shall be sealed in accordance with 501.15.Cablebus.In restricted industrial establishments, listed Type P cable with or without metal braid armor, with an overall jacket, and terminated with fittings listed for the location when entering explosionproof, flameproof, or pressurized equipment. The cable shall be installed in accordance with Part II of Article 337.Informational Note No. 2: See ANSI/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. [501.10(B)(1)](https://2023.antflix.net#501.10(B)(1)) | https://2023.antflix.net#501.10(B)(1) |
Chaptewr 5 Special Occupancies | 501.10(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 or more of the following shall be permitted: Listed flexible metal fittingsFlexible metal conduit with listed fittings and bonded in accordance with 501.30(B)Interlocked armor Type MC cable with listed fittingsLiquidtight flexible metal conduit with listed fittings and bonded in accordance with 501.30(B)Liquidtight flexible nonmetallic conduit with listed fittingsFlexible cord listed for extra-hard usage and terminated with listed fittings, with a conductor for use as an equipment grounding conductorFor 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 fittingsIn restricted industrial establishments, listed Type P cable with or without metal braid armor, with an overall jacket, terminated with listed fittings and installed in accordance with Part II of Article 337 [501.10(B)(2)](https://2023.antflix.net#501.10(B)(2)) | https://2023.antflix.net#501.10(B)(2) |
Chaptewr 5 Special Occupancies | 501.10(B)(3) | Nonincendive field wiring shall be permitted using any of the wiring methods permitted for unclassified locations. Nonincendive field wiring systems shall be installed in accordance with the control drawing(s). Simple apparatus, not shown on the control drawing, shall be permitted in a nonincendive field wiring circuit if the simple apparatus does not interconnect the nonincendive field wiring circuit to any other circuit. Informational Note: See Article 100 for the definition of simple apparatus. Separate nonincendive field wiring circuits 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 or in raceways, where the conductors of each circuit have insulation with a minimum thickness of 0.25 mm (0.01 in.) [501.10(B)(3)](https://2023.antflix.net#501.10(B)(3)) | https://2023.antflix.net#501.10(B)(3) |
Chaptewr 5 Special Occupancies | 501.10(B)(4) | Boxes and fittings shall be explosion-proof if required by 501.105(B)(2), 501.115(B)(1), or 501.150(B)(1). 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 cable for entry into enclosures required to be explosionproof. Informational Note No. 2: See ANSI/UL 1203, Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations, for information on construction, testing, and marking of explosionproof conduit fittings for entry into enclosures required to be explosionproof. [501.10(B)(4)](https://2023.antflix.net#501.10(B)(4)) | https://2023.antflix.net#501.10(B)(4) |
Chaptewr 5 Special Occupancies | 501.15 | Seals in conduit and cable systems shall comply with 501.15(A) through (F). 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: 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 MI 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 may be a slow passage of gas or vapor through a seal and through conductors passing through the seal. Temperature extremes and highly corrosive liquids and vapors can affect the ability of seals to perform their intended function. Informational Note No. 2: Gas or vapor leakage and propagation of flames may occur through the interstices between the strands of standard stranded conductors larger than 2 AWG. Special conductor constructions, such as compacted strands or sealing of the individual strands, are means of reducing leakage and preventing the propagation of flames. [501.15](https://2023.antflix.net#501.15) | https://2023.antflix.net#501.15 |
Chaptewr 5 Special Occupancies | 501.15(A) | In Class I, Division 1 locations, conduit seals shall be located in accordance with 501.15(A)(1) through (A)(4). [501.15(A)](https://2023.antflix.net#501.15(A)) | https://2023.antflix.net#501.15(A) |
Chaptewr 5 Special Occupancies | 501.15(A)(1) | Each conduit entry into an explosionproof enclosure shall have a conduit seal 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 temperatures that exceed 80 percent of the autoignition temperature, in degrees Celsius, of the gas or vapor involved in normal operation.Exception: Seals shall not be required for conduit entering an enclosure under any one of the following conditions:The switch, circuit breaker, fuse, relay, or resistor is enclosed within a chamber hermetically sealed against the entrance of gases or vapors.The switch, circuit breaker, fuse, relay, or resistor is immersed in oil in accordance with 501.115(B)(1)(2).The switch, circuit breaker, fuse, relay, or resistor is enclosed within an enclosure, identified for the location, and marked "Leads Factory Sealed," or "Factory Sealed," "Seal not Required," or equivalent.The switch, circuit breaker, fuse, relay, or resistor is part of a nonincendive circuit.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," or "Seal not Required," or equivalent shall not be considered to serve as a seal for another adjacent enclosure that is required to have a conduit seal.Conduit seals shall be installed within 450 mm (18 in.) from the enclosure or as required by the enclosure marking. 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. [501.15(A)(1)](https://2023.antflix.net#501.15(A)(1)) | https://2023.antflix.net#501.15(A)(1) |
Chaptewr 5 Special Occupancies | 501.15(A)(2) | Conduit seals shall be installed within 450 mm (18 in.) of the enclosure in each conduit entry into a pressurized enclosure where the conduit is not pressurized as part of the protection system. Informational Note No. 1: Installing the seal as close as possible to the enclosure will reduce 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 regarding pressurized enclosures. [501.15(A)(2)](https://2023.antflix.net#501.15(A)(2)) | https://2023.antflix.net#501.15(A)(2) |
Chaptewr 5 Special Occupancies | 501.15(A)(3) | Where two or more explosionproof enclosures that require conduit seals are connected by nipples or 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 the seal is located not more than 450 mm (18 in.) from either enclosure. [501.15(A)(3)](https://2023.antflix.net#501.15(A)(3)) | https://2023.antflix.net#501.15(A)(3) |
Chaptewr 5 Special Occupancies | 501.15(A)(4) | A conduit seal shall be required in each conduit run leaving a Division 1 location. The sealing fitting shall be permitted to be installed on either side of the boundary within 3.05 m (10 ft) of the boundary, and it shall be designed and installed to minimize the amount of gas or vapor within the portion of the conduit installed in the Division 1 location that can be communicated beyond the seal. The conduit run between the conduit seal and the point at which the conduit leaves the Division 1 location shall contain no union, coupling, box, or other fitting except for a listed explosionproof reducer installed at the conduit seal. Where the seal is located on the Division 2 side of the boundary, the Division 1 wiring method shall extend into the Division 2 area to the seal. Exception No. 1: Metal conduit that contains no unions, couplings, boxes, or fittings, that passes completely through a Division 1 location with no fittings installed within 300 mm (12 in.) of either side of the boundary, shall not require a conduit seal if the termination points of the unbroken conduit are located in unclassified locations. Exception No. 2: For underground conduit installed in accordance with 300.5 where the boundary is below grade, the sealing fitting shall be permitted to be installed after the conduit emerges from below grade, but there shall be no union, coupling, box, or fitting, other than listed explosionproof reducers at the sealing fitting, in the conduit between the sealing fitting and the point at which the conduit emerges from below grade. [501.15(A)(4)](https://2023.antflix.net#501.15(A)(4)) | https://2023.antflix.net#501.15(A)(4) |
Chaptewr 5 Special Occupancies | 501.15(B) | In Class I, Division 2 locations, conduit seals shall be located in accordance with 501.15(B)(1) and (B)(2). [501.15(B)](https://2023.antflix.net#501.15(B)) | https://2023.antflix.net#501.15(B) |
Chaptewr 5 Special Occupancies | 501.15(B)(1) | For connections to enclosures that are required to be explosionproof, a conduit seal shall be provided in accordance with 501.15(A)(1)(1) and (A)(3). All portions of the conduit run or nipple between the seal and enclosure shall comply with 501.10(A). [501.15(B)(1)](https://2023.antflix.net#501.15(B)(1)) | https://2023.antflix.net#501.15(B)(1) |
Chaptewr 5 Special Occupancies | 501.15(B)(2) | A conduit seal shall be required in each conduit run leaving a Class I. Division 2 location. The sealing fitting shall be permitted to be installed on either side of the boundary within 3.05 m (10 ft) of the boundary and it shall be designed and installed to minimize the amount of gas or vapor within the portion of the conduit installed in the Division 2 location that can be communicated beyond the seal. Wiring methods permitted in 501.10(B)(1)(1) or (B)(1)(6) shall be used between the sealing fitting and the point at which the conduit leaves the Division 2 location, and a threaded connection shall be used at the sealing fitting. The conduit run between the conduit seal and the point at which the conduit leaves the Division 2 location shall contain no union, coupling, box, or other fitting except for a listed explosionproof reducer installed at the conduit seal. Such seals shall not be required to be explosionproof but shall be identified for the purpose of minimizing the passage of gases permitted under normal operating conditions and shall be accessible. Informational Note No. 1: See ANSI/UL 514B, Conduit, Tubing, and Cable Fittings, for additional information. Exception No. 1: Metal conduit that contains no unions, couplings, boxes, or fittings and that passes completely through a Division 2 location with no fittings installed within 300 mm (12 in.) of either side of the boundary shall not require a seal if the termination points of the unbroken conduit are located in unclassified locations. Exception No. 2: Conduit terminating in an unclassified location where the metal conduit transitions to cable tray, cablebus, ventilated busway, or Type MI cable, or to cable not installed in any cable tray or raceway system, shall not require a seal where passing from the Division 2 location into the unclassified location under the following conditions: (1) The unclassified location is outdoors, or the unclassified location is indoors and the conduit system is entirely in one room. (2) The conduits do not terminate at an enclosure containing an ignition source in normal operation. Exception No. 3: Conduit passing from an enclosure or a room permitted to use general-purpose equipment as a result of pressurization into a Division 2 location shall not require a seal at the boundary. Informational Note No. 2: See NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment, for further information. Exception No. 4: Aboveground conduit shall not require a seal where passing from a Division 2 location into an unclassified location if all of the following conditions are met: (1) No part of the conduit passes through a Division 1 location where the conduit contains unions, couplings, boxes, or fittings that are located within 300 mm (12 in.) of the Division 1 location. (2) The conduit is located entirely outdoors. (3) The conduit is not 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. (4) The conduit contains only threaded metal conduit, unions, couplings, conduit bodies, and fillings in the unclassified location. (5) The conduit is sealed at its entry to each enclosure or fitting located in the Division 2 location that contains terminals, splices, or taps. [501.15(B)(2)](https://2023.antflix.net#501.15(B)(2)) | https://2023.antflix.net#501.15(B)(2) |
Chaptewr 5 Special Occupancies | 501.15(C) | Seals installed in Class I, Division 1 and Division 2 locations shall comply with 501.15(C)(1) through (C)(6). Exception: Seals that are not required to be explosionproof by 501.15(B)(2) or 504. 70 shall not be required to comply with 501.15(C). [501.15(C)](https://2023.antflix.net#501.15(C)) | https://2023.antflix.net#501.15(C) |
Chaptewr 5 Special Occupancies | 501.15(C)(1) | Enclosures that contain connections or equipment shall be provided with an integral sealing means, 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. [501.15(C)(1)](https://2023.antflix.net#501.15(C)(1)) | https://2023.antflix.net#501.15(C)(1) |
Chaptewr 5 Special Occupancies | 501.15(C)(2) | The compound shall provide a seal to minimize the passage of gas and/or vapors through the sealing fitting and shall not be affected by the surrounding atmosphere or liquids. The melting point of the compound shall not be less than 93°C (200°F). [501.15(C)(2)](https://2023.antflix.net#501.15(C)(2)) | https://2023.antflix.net#501.15(C)(2) |
Chaptewr 5 Special Occupancies | 501.15(C)(3) | The thickness of the sealing compound installed in completed seals, other than listed cable sealing fittings, shall not be less than the metric designator (trade size) of the sealing fitting expressed in the units of measurement employed; however, in no case shall the thickness of the compound be less than 16 mm (5/8 in.). [501.15(C)(3)](https://2023.antflix.net#501.15(C)(3)) | https://2023.antflix.net#501.15(C)(3) |
Chaptewr 5 Special Occupancies | 501.15(C)(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. [501.15(C)(4)](https://2023.antflix.net#501.15(C)(4)) | https://2023.antflix.net#501.15(C)(4) |
Chaptewr 5 Special Occupancies | 501.15(C)(5) | An entire assembly shall be identified for the location where the equipment that may produce arcs, sparks, or high temperatures is located in a compartment that is separate from the compartment containing splices or taps, and an integral seal is provided where conductors pass from one compartment to the other. In Division 1 locations, seals shall be provided in conduit connecting to the compartment containing splices or taps where required by 501.15(A)(1)(2). [501.15(C)(5)](https://2023.antflix.net#501.15(C)(5)) | https://2023.antflix.net#501.15(C)(5) |
Chaptewr 5 Special Occupancies | 501.15(C)(6) | 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 the seal is specifically identified for a higher percentage of fill. [501.15(C)(6)](https://2023.antflix.net#501.15(C)(6)) | https://2023.antflix.net#501.15(C)(6) |
Chaptewr 5 Special Occupancies | 501.15(D) | In Division 1 locations, cable seals shall be located according to 501.15(D)(1) through (D)(3). [501.15(D)](https://2023.antflix.net#501.15(D)) | https://2023.antflix.net#501.15(D) |
Chaptewr 5 Special Occupancies | 501.15(D)(1) | Cables shall be sealed at all terminations with sealing fittings. The seals at all terminations shall be in accordance with 501.15(C) and shall be installed within 450 mm (18 in.) of the enclosure or as required by the enclosure marking. Only threaded couplings or explosionproof fittings such as unions, reducers, elbows, and capped elbows not larger than the trade size of the conduit shall be permitted between the sealing fitting and the enclosure. Type MC-HL cable with a gas/vaportight continuous corrugated metallic sheath and an overall jacket of suitable polymeric material, Type TC-ER-HL cable, and Type P cable shall be sealed with a listed fitting after the jacket and any other covering have been removed so that the sealing compound can surround each individual insulated conductor to minimize the passage of gases and vapors. Shielded cables and twisted pair cables that have their conductors sealed in accordance with the instructions provided with their listed fitting to minimize the entrance of gases or vapors and prevent propagation of flame into the cable core shall not be required to have the shielding material removed or the twisted pairs separated. [501.15(D)(1)](https://2023.antflix.net#501.15(D)(1)) | https://2023.antflix.net#501.15(D)(1) |
Chaptewr 5 Special Occupancies | 501.15(D)(2) | Cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core, installed in conduit, shall be sealed in the Class I, Division 1 location after the jacket and any other coverings have been removed such that the sealing compound can surround 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 a single conductor if the cable is sealed in the conduit within 450 mm (18 in.) of the enclosure and the cable end is sealed 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. If both requirements are met, the shielding material shall not be required to be removed and the twisted pairs of shielded cables and twisted pair cables shall not be required to be separated. [501.15(D)(2)](https://2023.antflix.net#501.15(D)(2)) | https://2023.antflix.net#501.15(D)(2) |
Chaptewr 5 Special Occupancies | 501.15(D)(3) | Each multiconductor cable installed in conduit shall be considered as a single conductor if the cable is incapable of transmitting gases or vapors through the cable core. These cables shall be sealed in accordance with 501.15(A). [501.15(D)(3)](https://2023.antflix.net#501.15(D)(3)) | https://2023.antflix.net#501.15(D)(3) |
Chaptewr 5 Special Occupancies | 501.15(E) | In Division 2 locations, cable seals shall be located in accordance with 501.15(E)(1) through (E)(4). Exception: Cables with an unbroken gas/vaportight, continuous sheath shall be permitted to pass through a Division 2 location without seals. [501.15(E)](https://2023.antflix.net#501.15(E)) | https://2023.antflix.net#501.15(E) |
Chaptewr 5 Special Occupancies | 501.15(E)(1) | Cables entering enclosures that are required to be explosionproof shall be sealed at the point of entrance into the enclosure. The sealing fitting shall comply with 501.15(B)(1) or be explosionproof. Multiconductor or optical multifiber cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core that are installed in a Division 2 location shall be sealed with a listed fitting after the jacket and any other coverings have been removed 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 installed in conduit shall be sealed in accordance with 501.15(D). Exception No. 1: Cables leaving art enclosure or room that is permitted to use general-purpose equipment as a result of Type Z pressurization and entering a Division 2 location shall not require a seal at the boundary. Exception No. 2: Removal of shielding material from shielded cables and separation of twisted pair cables shall not be required if the conductors are sealed in accordance with instructions provided with the listed fitting to minimize the entrance of gases or vapors and prevent propagation of flame into the cable core. [501.15(E)(1)](https://2023.antflix.net#501.15(E)(1)) | https://2023.antflix.net#501.15(E)(1) |
Chaptewr 5 Special Occupancies | 501.15(E)(2) | Cables that have a gas/vaportight continuous sheath and do 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 501.15(E)(1). The minimum length of such a cable run shall not be less than the length needed to limit gas or vapor flow through the cable core, excluding the interstices of the conductor strands, 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)]. [501.15(E)(2)](https://2023.antflix.net#501.15(E)(2)) | https://2023.antflix.net#501.15(E)(2) |
Chaptewr 5 Special Occupancies | 501.15(E)(3) | 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 501.15(E)(1), unless the cable is attached to process equipment or devices that may cause a pressure in excess of 1500 pascals (6 in. of water) to be exerted at a cable end, in which case a seal, a barrier, or other means shall be provided to prevent migration of flammables into an unclassified location. [501.15(E)(3)](https://2023.antflix.net#501.15(E)(3)) | https://2023.antflix.net#501.15(E)(3) |
Chaptewr 5 Special Occupancies | 501.15(E)(4) | Cables that do not have a gas/vaportight continuous sheath shall be sealed at the boundary of the Division 2 and unclassified location in such a manner as to minimize the passage of gases or vapors into an unclassified location. [501.15(E)(4)](https://2023.antflix.net#501.15(E)(4)) | https://2023.antflix.net#501.15(E)(4) |
Chaptewr 5 Special Occupancies | 501.15(F)(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. [501.15(F)(1)](https://2023.antflix.net#501.15(F)(1)) | https://2023.antflix.net#501.15(F)(1) |
Chaptewr 5 Special Occupancies | 501.15(F)(2) | Where liquid or condensed vapor may accumulate within motors or generators, joints and conduit systems shall be arranged to minimize the 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. [501.15(F)(2)](https://2023.antflix.net#501.15(F)(2)) | https://2023.antflix.net#501.15(F)(2) |
Chaptewr 5 Special Occupancies | 501.17 | Process-connected equipment, including, but not limited to, canned pumps, submersible pumps, and flow, pressure, temperature, or analysis measurement instruments, shall be sealed with process seals. A process seal shall be a device that prevents 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 are not limited to, the following: A suitable barrier meeting the process temperature and pressure conditions that the barrier will be subjected to 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 501.15.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. [501.17](https://2023.antflix.net#501.17) | https://2023.antflix.net#501.17 |
Chaptewr 5 Special Occupancies | 501.20 | 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. [501.20](https://2023.antflix.net#501.20) | https://2023.antflix.net#501.20 |
Chaptewr 5 Special Occupancies | 501.25 | 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 a protection technique according to 500.7(E), (F), or (G) that is suitable for the location. [501.25](https://2023.antflix.net#501.25) | https://2023.antflix.net#501.25 |
Chaptewr 5 Special Occupancies | 501.30 | Regardless of the voltage of the electrical system, wiring systems and equipment shall comply with 501.30(A) and (B). [501.30](https://2023.antflix.net#501.30) | https://2023.antflix.net#501.30 |
Chaptewr 5 Special Occupancies | 501.30(A) | Wiring systems and equipment shall be grounded in accordance with Part I and Part VI of Article 250, as applicable. [501.30(A)](https://2023.antflix.net#501.30(A)) | https://2023.antflix.net#501.30(A) |
Chaptewr 5 Special Occupancies | 501.30(B) | Bonding shall comply with Part I and Part V of Article 250, as applicable, and 501.30(B)(1) and (B)(2). [501.30(B)](https://2023.antflix.net#501.30(B)) | https://2023.antflix.net#501.30(B) |
Chaptewr 5 Special Occupancies | 501.30(B)(1) | Bonding shall comply with 501.30(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 Class I 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). [501.30(B)(1)](https://2023.antflix.net#501.30(B)(1)) | https://2023.antflix.net#501.30(B)(1) |
Chaptewr 5 Special Occupancies | 501.30(B)(2) | Flexible metal conduit and liquidtight flexible metal conduit shall comply with 501.30(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 Class I, Division 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. [501.30(B)(2)](https://2023.antflix.net#501.30(B)(2)) | https://2023.antflix.net#501.30(B)(2) |
Chaptewr 5 Special Occupancies | 501.35(A) | Surge arresters, surge-protective devices, and capacitors shall be installed in enclosures identified for Class I, Division 1 locations. Surge-protective capacitors shall be of a type designed for specific duty. [501.35(A)](https://2023.antflix.net#501.35(A)) | https://2023.antflix.net#501.35(A) |
Chaptewr 5 Special Occupancies | 501.35(B) | Surge arresters and surge-protective devices shall be nonarcing, such as metal-oxide varistor (MOV) sealed type, and surge-protective capacitors shall be of a type designed for specific duty. Enclosures shall be permitted to be of the general-purpose type. Surge protection of types other than described in this paragraph shall be installed in enclosures identified for Class I, Division 1 locations. [501.35(B)](https://2023.antflix.net#501.35(B)) | https://2023.antflix.net#501.35(B) |
Chaptewr 5 Special Occupancies | 501.100(A) | In Class I, Division 1 locations, transformers and capacitors shall comply with 501.100(A)(1) and (A)(2). [501.100(A)](https://2023.antflix.net#501.100(A)) | https://2023.antflix.net#501.100(A) |
Chaptewr 5 Special Occupancies | 501.100(A)(1) | Transformers and capacitors containing a liquid that will burn shall be installed only in vaults that comply with 450.41 through 450.48 and with (1) through (4) as follows: There shall be no door or other communicating opening between the vault and the Division 1 location.Ample ventilation shall be provided for the continuous removal of flammable gases or vapors.Vent openings or ducts shall lead to a safe location outside of buildings.Vent ducts and openings shall be of sufficient area to relieve explosion pressures within the vault, and all portions of vent ducts within the buildings shall be of reinforced concrete construction. [501.100(A)(1)](https://2023.antflix.net#501.100(A)(1)) | https://2023.antflix.net#501.100(A)(1) |
Chaptewr 5 Special Occupancies | 501.100(A)(2) | Transformers and capacitors that do not contain a liquid that will burn shall be installed in vaults complying with 501.100(A)(1) or be identified for Class I locations. [501.100(A)(2)](https://2023.antflix.net#501.100(A)(2)) | https://2023.antflix.net#501.100(A)(2) |
Chaptewr 5 Special Occupancies | 501.100(B) | In Class I, Division 2 locations, transformers shall comply with 450.21 through 450.27, and capacitors shall comply with 460.3 through 460.28. [501.100(B)](https://2023.antflix.net#501.100(B)) | https://2023.antflix.net#501.100(B) |
Chaptewr 5 Special Occupancies | 501.105(A) | In Class I, Division 1 locations, meters, instruments, and relays, including kilowatt-hour meters, instrument transformers, resistors, rectifiers, and thermionic tubes, shall be provided with enclosures identified for Class I, Division 1 locations. Enclosures for Class I, Division 1 locations include explosionproof enclosures and purged and pressurized enclosures. Informational Note: See NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment. [501.105(A)](https://2023.antflix.net#501.105(A)) | https://2023.antflix.net#501.105(A) |
Chaptewr 5 Special Occupancies | 501.105(B) | In Class I, Division 2 locations, meters, instruments, and relays shall comply with 501.105(B)(2) through (B)(6). [501.105(B)](https://2023.antflix.net#501.105(B)) | https://2023.antflix.net#501.105(B) |
Chaptewr 5 Special Occupancies | 501.105(B)(1) | Where an assembly is made up of components for which general-purpose enclosures are acceptable as provided in 501.105(B)(1), (B)(2), and (B)(3), a single general-purpose enclosure shall be acceptable for the assembly. Where such an assembly includes any of the equipment described in 501.105(B)(1), 501.105(B)(2), and 501.105(B)(3), the maximum obtainable surface temperature of any component of the assembly that exceeds 100°C shall be clearly and permanently indicated on the outside of the enclosure. Alternatively, equipment shall be permitted to be marked to indicate the temperature class for which it is suitable, using the temperature class (T Code) of Table 500.8(C)(4). [501.105(B)(1)](https://2023.antflix.net#501.105(B)(1)) | https://2023.antflix.net#501.105(B)(1) |
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