Text/031.txt

CHAPTER 7
COMBUSTION
, VENTILATION, AND DILUTION
AIR
SECTION MC 701
GENERAL
701.1 Scope. 
The
provisions of this chapter shall govern the requirements for combustion, ventilation, and dilution 
air for fuel
-
burning appliances other than gas
-
fired appliances. The requirements for combustion, ventilation, and 
dilution air for gas
-
fired appliances shal
l be in accordance with 
the New York City Fuel Gas Code.
701.2 Combustion, ventilation, and dilution air required.
Every room or space containing fuel
-
burning appliances 
shall be provided with combustion, ventilation, and dilution air as required by this c
ode. Combustion, ventilation, 
and dilution air shall be provided in accordance with Section 702, 703, 704, 705, 706 or 707. Direct
-
vent appliances 
or equipment that do not draw combustion air from inside of the building are not required to be considered in
the 
determination of the combustion and dilution air requirements and shall be installed in accordance with the equip-
ment manufacturer’s instructions and listing. Combustion air requirements shall be determined based on the simul-
taneous operation of all f
uel
-
burning appliances drawing combustion, ventilation, and dilution air from the room or 
space. Combustion, ventilation, and dilution air shall be obtained solely from the outdoors for fuel
-
burning appli-
ances with an input greater than 350,000 Btu/h (102.
6 kW). The room or space containing fuel
-
burning appliances 
shall comply with the requirements of Sections C402.5.3 and R402.4.4, as applicable, of the 
New York City Energy 
Conservation Code
and Section 1012 of this code.
701.3 Circulation of air.
The equi
pment and appliances within every room containing fuel
-
burning appliances shall 
be installed so as to allow free circulation of air. Provisions shall be made to allow for the simultaneous operation of 
mechanical exhaust systems, fireplaces or other equipme
nt and appliances operating in the same room or space from 
which combustion, ventilation, and dilution air is being drawn. Such provisions shall prevent the operation of such 
appliances, equipment and systems from affecting the supply of combustion, ventil
ation, and dilution air.
701.3.1 Makeup air for fuel
-
burning devices.
Where exhaust fans are installed, makeup air shall be provided to 
replace the exhausted air. Calculations shall be provided on the construction documents to validate the use of the 
exhaust fan(s) and compliance with this chapter.
701.3.2 Ventilation air f
or fuel
-
burning devices.
Where ventilation air is brought in by mechanical means for 
heat generation mitigation, provisions must be made for proper air balance to prevent a negative or positive pressure 
in the boiler and to discharge the ventilation air di
rectly to the outside.
701.4 Crawl space and attic space. 
For the purposes of this chapter, an opening to a naturally ventilated crawl space 
or attic space shall be considered equivalent to an opening to the outdoors.
701.4.1 Crawl space.
Where lower combu
stion air openings connect with crawl spaces, such spaces shall have 
unobstructed openings to the outdoors at least twice that required for the 
combustion air openings
. The height of 
the crawl space shall comply with the requirements of the 
New York City B
uilding Code 
and shall be without 
obstruction to the free flow of air.
701.4.2 Attic space.
Where combustion air is obtained from an attic area, the attic ventilating openings shall not 
be subject to ice or snow blockage, and the attic shall have not less 
than 30 inches (762 mm) vertical clear height 
at its maxi
-
mum point. Attic ventilation openings shall be sufficient to provide the required volume of combustion 
air and the attic ventilation required by the 
New York City Building Code.
The combustion air o
penings shall be 
provided with a sleeve of not less than 0.019 inch (0.48 mm) (No.26 Gage) galvanized steel or other approved 
material extending from the appliance enclosure to at least 6 inches (
152.4
mm) above the top of the ceiling joists 
and insulation
.
701.5 Prohibited sources.
Openings and ducts shall not connect appliance enclosures with a space in which the 
operation of a fan will adversely affect the flow of the combustion, ventilation, and dilution air. Combustion, venti-
lation, and dilution air sh
all not be subject to ice or snow blockage. No combustion, ventilation, and dilution air inlet 
COMBUSTION, VENTILATION, AND DILUTION AIR
shall be less than 30 inches (762 mm) above grade. Combustion, ventilation, and dilution air shall not be obtained 
from a hazardous location, except where the fu
el
-
fired appliances are located within the hazardous location and are 
installed in accordance with this code. Combustion, ventilation, and dilution air shall not be taken from a refrigeration 
machinery room, except where a refrigerant vapor detector system
is installed to automatically shut off the combus-
tion process in the event of refrigerant leakage. For structures in flood hazard areas, air shall be obtained from a 
location complying with the additional requirements of Appendix G of the 
New York City Bu
ilding Code.
SECTION MC 702
INSIDE AIR
702.1 All air from indoors.
Combustion, ventilation, and dilution air shall be permitted to be obtained entirely from 
the indoors in buildings that are not of unusually tight construction. In buildings of 
unusually tight construction, 
combustion air shall be obtained from the outdoors in accordance with Section 703, 705, 706 or 707.
702.2 Air from the same room or space.
The room or space containing fuel
-
burning appliances shall be an uncon-
fined space as de
fined in Section 202.
702.3 Air from adjacent spaces.
Where the volume of the room in which the fuel
-
burning appliances are located 
does not comply with Section 702.2, additional inside combustion, ventilation, and dilution air shall be obtained by 
opening
the room to adjacent spaces so that the combined volume of all communicating spaces meets the volumetric 
requirement of Section 702.2. Openings connecting the spaces shall comply with Sections 702.3.1, 702.3.2 and Fig-
ure A
-
1 of Appendix A.
702.3.1 Number 
and location of openings.
Two openings shall be provided, one within 1 foot (
304.8
mm) of the 
ceiling of the room and one within 1 foot (
304.8
mm) of the floor.
702.3.2 Size of openings.
The net free area of each opening, calculated in accordance with Sect
ion 708, shall be 
a minimum of 1 square inch per 1,000 Btu/h (2201 mm
2
/kW) of input rating of the fuel
-
burning appliances draw-
ing combustion, ventilation, and dilution air from the communicating spaces and shall be not less than 100 square 
inches (64 516 m
m
2
).
SECTION MC 703
OUTDOOR AIR
703.1 All air from the outdoors.
Where all combustion, ventilation, and dilution air is to be provided by outdoor 
air, the required combustion, ventilation, and dilution air shall be obtained by direct opening by louver or a
duct(s) 
from the boiler room to the outdoors. Openings connecting the room to the outdoor air shall comply with Sections 
703.1.1 through 703.1.2    of this code, and Figures 304.6.1(1), 304.6.1(2), 304.6.1(3) and 304.6.2 of 
the New York 
City Fuel Gas Code
. 
The size of the openings connecting the room to the outdoor air supply shall also comply with 
any applicable rules of the New York City Department of Environmental Protection.
703.1.1 Two
-
permanent
-
openings method.
Two permanent openings, one commencing within 12 inches (304.8 
mm) at the top and one commencing within 12 inches (304.8 mm) of the bottom of the room, shall be provided. 
The openings shall communicate directly, or by ducts, with the outdoors or spaces th
at freely communicate with 
the outdoors as follows:
1.
Where directly communicating with the outdoors, or where communicating with the outdoors through verti-
cal ducts, each opening shall have a minimum free area of 1 square inch per 4,000 Btu/h (550 mm
2
/kW
) of 
total input rating of all equipment in the room.
2.
Where communicating with the outdoors through horizontal ducts, each opening shall have a minimum free 
area of not less than 1 square inch per 2,000 Btu/H (1100 mm
2
/kW) of total input rating of all e
quipment in 
the room. 
703.1.2 One
-
permanent
-
opening method.
One permanent opening, commencing within 12 inches (304.8 mm) of 
the top of the enclosure, shall be provided. The equipment shall have clearances of at least 1 inch (25.4 mm) from 
the sides and b
ack and 6 inches (152.4 mm) from the front of the appliance. The opening shall directly communicate 
with the outdoors or through a vertical or horizontal duct to the outdoors or spaces that freely communicate with 
mm) at the top and one commencing within 12 inches (304.8 mm) of the bottom of the room, shall be provided. 
The openings shall communicate directly, or by ducts, with the outdoors or spaces th
at freely communicate with 
the outdoors as follows:
1.
Where directly communicating with the outdoors, or where communicating with the outdoors through verti-
cal ducts, each opening shall have a minimum free area of 1 square inch per 4,000 Btu/h (550 mm
2
/kW
) of 
total input rating of all equipment in the room.
2.
Where communicating with the outdoors through horizontal ducts, each opening shall have a minimum free 
area of not less than 1 square inch per 2,000 Btu/H (1100 mm
2
/kW) of total input rating of all e
quipment in 
the room. 
703.1.2 One
-
permanent
-
opening method.
One permanent opening, commencing within 12 inches (304.8 mm) of 
the top of the enclosure, shall be provided. The equipment shall have clearances of at least 1 inch (25.4 mm) from 
the sides and b
ack and 6 inches (152.4 mm) from the front of the appliance. The opening shall directly communicate 
with the outdoors or through a vertical or horizontal duct to the outdoors or spaces that freely communicate with 
COMBUSTION, VENTILATION, AND DILUTION AIR
the outdoors and shall have a minimum free
area of 1 square inch per 3,000 Btu/h (734 mm
2
/kW) of the total input 
rating of all equipment located in the enclosure, and not less than the sum of the areas of all vent connectors in the 
space.
SECTION MC 704
COMBINED USE OF INSIDE AND OUTDOOR AIR
(COND
ITION 1)
704.1 Combination of air from inside and outdoors.
This section shall apply only to appliances located in confined 
spaces in buildings not of unusually tight construction. Where the volumes of rooms and spaces are combined for 
the purpose of provi
ding indoor combustion air, such rooms and spaces shall communicate through permanent open-
ings in compliance with Sections 702.3.1 and 702.3.2. The required combustion, ventilation, and dilution air shall 
be obtained by opening the room to the outdoors usi
ng a combination of inside and outdoor air, prorated in accord-
ance with Section 704.1.6. The ratio of interior spaces shall comply with Section 704.1.5. The number, location and 
ratios of openings connecting the space with the outdoor air shall comply with
Sections 704.1.1 through 704.1.4.
704.1.1 Number and location of openings.
At least two openings shall be provided, one within 1 foot (
304.8
mm) of the ceiling of the room and one within 1 foot (
304.8
mm) of the floor.
704.1.2 Ratio of direct openings.
Wh
ere direct openings to the outdoors are provided in accordance with Section 
703.1, the ratio of direct openings shall be the sum of the net free areas of both direct openings to the outdoors, 
divided by the sum of the required areas for both such openings 
as determined in accordance with Section 703.1.2.
704.1.3 Ratio of horizontal openings.
Where openings connected to the outdoors through horizontal ducts are 
pro
-
vided in accordance with Section 703.1, the ratio of horizontal openings shall be the sum of 
the net free areas 
of both such openings, divided by the sum of the required areas for both such openings as determined in accord-
ance with Section 703.1.3.
704.1.4 Ratio of vertical openings.
Where openings connected to the outdoors through vertical ducts 
are provided 
in accordance with Section 703.1, the ratio of vertical openings shall be the sum of the net free areas of both such 
openings, divided by the sum of the required areas for both such openings as determined in accordance with 
Section 703.1.4.
70
4.1.5 Ratio of interior spaces.
The ratio of interior spaces shall be the available volume of all communicating 
spaces, divided by the required volume as determined in accordance with Sections 702.2 and 702.3.
704.1.6 Prorating of inside and outdoor air.
In spaces that utilize a combination of inside and outdoor air, the 
sum of the ratios of all direct openings, horizontal openings, vertical openings and interior spaces shall equal or 
exceed 1.
SECTION MC 705
COMBINED USE OF INSIDE AND OUTDOOR AIR
(CONDITI
ON 2)
705.1 General.
This section shall apply only to appliances located in unconfined spaces in buildings of unusually 
tight construction. Combustion air supplied by a combined use of indoor and outdoor air shall be supplied through 
openings and ducts ext
ending to the appliance room or to the vicinity of the appliance.
705.1.1 Openings and supply ducts.
Openings shall be provided, located and sized in accordance with Sections 
702.3.1 and 702.3.2; additionally, there shall be one opening to the outdoors hav
ing a free area of at least 1 square 
inch per 5,000 Btu/h (440 mm
2
/kW) of total input of all appliances in the space.
SECTION MC 706
MECHANICAL COMBUSTION AIR SUPPLY
706.1 Rate of air supplied.
Where all combustion air is provided by a mechanical air suppl
y system, the combustion 
air shall be supplied from the outdoors at a rate of not less than 0.35 cubic feet per minute per 1,000 Btu/h (0.034 
COMBUSTION, VENTILATION, AND DILUTION AIR
m
3
/min per kW) of total input rating for all the fuel
-
burning appliances located within the space. Combustion air 
rates shall also comply with any applicable rules of the New York City Department of Environmental Protection. 
The mechanical air supply shall be sufficient to accommodate combustion air, ventilation air, and dilution air re-
quirements of the installation.
706.1.1 Appliance interlock.
Each of the appliances served shall be interlocked with the mechanical air supply 
system to prevent main burner operation when the mechanical air supply system is not in operation. The air flow 
and the damper operation shall be
proven prior to burner operation.
SECTION MC 707
DIRECT CONNECTION
707.1 General.
Fuel
-
burning appliances that are listed and labeled for direct combustion air connection to the out-
doors shall be installed in accordance with the manufacturer’s instruction
s.
SECTION MC 708
COMBUSTION AIR DUCTS
708.1 General.
Combustion air ducts shall comply with all of the following:
1.
Be of galvanized steel complying with Chapter 6 or of equivalent corrosion
-
resistant material approved for 
this application.
Exception:
Within dwelling units, unobstructed stud and joist spaces shall not be prohibited from conveying 
combustion air, provided that not more than one required fireblock is removed.
2.
Have a minimum dimension of 3 inches (
76.2
mm) in all directions.
3.
Termin
ate in an unobstructed space allowing free movement of combustion air to the appliances.
4.
Have the same cross
-
sectional areas as the free area of the openings to which they connect.
5.
Serve a single appliance enclosure.
6.
Not serve both upper and lo
wer combustion air openings where both such openings are used. The separation 
between ducts serving upper and lower combustion air openings shall be maintained to the source of combus-
tion air.
7.
Not be screened where terminating in an attic space.
8.
No
t slope downward toward the source of combustion air, where serving the upper required combustion air 
opening.
9.
Be constructed so that the remaining space surrounding a chimney or chimney liner, installed within a masonry, 
metal or factory
-
built chimney
cannot be used to supply combustion, ventilation and dilution air, except for 
direct vent appliances designed and installed in accordance with the equipment manufacturer’s instructions 
and listing.
10.
Be insulated in accordance with Section C402.5.3 of t
he 
New York City Energy Conservation Code
.
SECTION MC 709
OPENING OBSTRUCTIONS
709.1 General.
The required size of openings for combustion, ventilation, and dilution air shall be based on the net 
free area of each opening. The net free area of an opening s
hall be that specified by the manufacturer of the opening 
covering. In the absence of such information, openings covered with metal louvers shall be deemed to have a net 
free area of 60 percent of the area of the opening, and openings covered with wood lou
vers shall be deemed to have 
a net free area of 10 percent of the area of the opening. Louvers and grills shall be fixed in the open position.
Exception:
Operable louvers shall be interlocked with the appliance so that they are proven to be in the full open 
position prior to main burner ignition and during main burner operation. Means shall be provided to prevent the 
COMBUSTION, VENTILATION, AND DILUTION AIR
main burner from igniting if the louvers
fail to open during burner startup and to shut down the main burner if the 
louvers close during operation.
709.2 Dampered openings.
Where the combustion air openings are provided with automatic, smoke or fire dampers, 
the dampers shall be 
electrically interlocked with the appliances served, so as to prevent operation of any appliance 
that draws combustion and dilution air from the room when any of the dampers are closed. Manually operated damp-
ers shall not be installed in combustion air ope
nings. The damper opening shall be proven prior to burner operation
. 
Dampers shall be provided in accordance with Chapter 6.
709.3 Caution sign.
A sign stating, “Louvers, dampers and/or ventilation openings must not be blocked or disabled.” 
shall be perman
ently affixed, in clear view, and adjacent to the opening(s) within the room containing the equipment. 
The letters used on the sign shall be at least 1 inch (
25.4
mm) in height.
SECTION MC 710
OPENING LOCATION AND PROTECTION
710.1 General.
Combustion air o
penings to the outdoors shall comply with the location and protection provisions 
applicable to outside air intake openings of Sections 401.5 and 401.6.