Chapter 5 Exhaust Systems

Exhaust openings that terminate outdoors shall be protected with corrosion-resistant screens, louvers or grilles. Openings in screens, louvers and grilles shall be sized not less than ¹/₄ inch (6.4 mm) and not larger than ¹/₂ inch (12.7 mm). Openings shall be protected against local weather conditions. Louvers that protect exhaust openings in structures located in hurricane-prone regions, as defined in the International Building Code, shall comply with AMCA Standard 550. Outdoor openings located in exterior walls shall meet the provisions for exterior wall opening protectives in accordance with the International Building Code.

Makeup air quantity for new dwellings shall be determined by using Table 501.4.1 and shall be supplied in accordance with section 501.4.2.

Table 501.4.1
Procedure to Determine Makeup Air Quantity for Exhaust Appliances in Dwellings

	One or multiple power vent or direct vent appliances or no combustion appliancesA	One or multiple fan-assisted appliances and power vent or direct vent appliancesB	One atmospherically vented gas or oil appliance or one solid fuel applianceC	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliancesD
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor (cfm/sf)	0.15	0.09	0.06	0.03
b) conditioned floor area (sf)	______	______	______	______
(including unfinished basements)
Estimated House Infiltration (cfm): [1a x 1b]	______	______	______	______
2. Exhaust Capacity
a) clothes dryer	135	135	135	135
b) 80% of largest exhaust rating (cfm):	______	______	______	______
(not applicable if recirculating system or if powered makeup air is electrically interlocked and matched to exhaust)
c) 80% of next largest exhaust rating (cfm):	not applicable	______	______	______
(not applicable if recirculating system or if powered makeup air is electrically interlocked and matched to exhaust)
Total Exhaust Capacity (cfm): [2a+2b+2c]	______	______	______	______
3. Makeup Air Requirement
a) Total Exhaust Capacity (from above)	______	______	______	______
b) Estimated House Infiltration (from above)	______	______	______	______
Makeup Air Quantity (cfm): [3a - 3b]	______	______	______	______
(if value is negative, no makeup air is needed)
4. For Makeup Air Opening Sizing, refer to Table 501.4.2

^A Use this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.

^B Use this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.

^C Use this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.

^D Use this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliances.

Makeup air shall be provided by one of the following methods:

Table 501.4.2
Makeup Air Opening Sizing Table for New and Existing Dwellings

Type of opening or system	One or multiple power vent or direct vent appliances or no combustion appliancesA	One or multiple fan-assisted  appliances and power vent or direct vent appliancesB	One atmospherically vented gas or oil appliance or one solid fuel applianceC	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliancesD	Passive makeup air opening duct diameterE,F,G
	(cfm)	(cfm)	(cfm)	(cfm)	(inches)
Passive Opening	1-36	1-22	1-15	1-9	3
Passive Opening	37-66	23-41	16-28	10-17	4
Passive Opening	67-109	42-66	29-46	18-28	5
Passive Opening	110-163	67-100	47-69	29-42	6
Passive Opening	164-232	101-143	70-99	43-61	7
Passive Opening	233-317	144-195	100-135	62-83	8
Passive Opening with Motorized Damper	318-419	196-258	136-179	84-110	9
Passive Opening with Motorized Damper	420-539	259-332	180-230	111-142	10
Passive Opening with Motorized Damper	540-679	333-419	231-290	143-179	11
Powered Makeup AirH	>679	>419	>290	>179	Not Applicable

^A Use this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.

^B Use this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.

^C Use this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.

^D Use this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliance(s).

^E An equivalent length of 100 feet of round smooth metal duct is assumed. Subtract 40 feet for the exterior hood and ten feet for each 90-degree elbow to determine the remaining length of straight duct allowable.

^F If flexible duct is used, increase the duct diameter by one inch. Flexible duct shall be stretched with minimal sags.

^G Barometric dampers are prohibited in passive makeup air openings when any atmospherically vented appliance is installed.

^H Powered makeup air shall be electrically interlocked with the largest exhaust system.

Makeup air shall be supplied to existing dwellings when any of the following conditions occur:

Table 501.4.3(1)
Procedure to Determine Makeup Air Quantity for Exhaust Appliancesin Existing Dwellings
(Refer to item 4 in section 501.4.3 to determine applicability of this table)

	One or multiple power vent or direct vent appliances or no combustion appliancesA	One or multiple fan-assisted appliances and power vent or direct vent appliancesB	One atmospherically vented gas or oil appliance or one solid fuel applianceC	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliancesD
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor (cfm/sf)	0.15	0.09	0.06	0.03
b) conditioned floor area (sf)	_____	_____	_____	_____
Estimated House Infiltration (cfm): [1a x 1b]	_____	_____	_____	_____
2. Exhaust Capacity
80% of exhaust rating = Exhaust Capacity (cfm):	_____	_____	_____	_____
(not applicable if recirculating system or if powered makeup air is electrically interlocked and matched to exhaust)
3. Makeup Air Requirement
a) Exhaust Capacity (from above)	_____	_____	_____	_____
b) Estimated House Infiltration (from above)	_____	_____	_____	_____
Makeup Air Quantity (cfm): [3a - 3b]	_____	_____	_____	_____
(if value is negative, no makeup air is needed)
4. For Makeup Air Opening Sizing, refer to Table 501.4.2

1. Use this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.
2. Use this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.
3. Use this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.
4. Use this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliances.

Table 501.4.3(2)
Procedure to Determine Makeup Air Quantity for Exhaust Appliances in Existing Dwellings
(Refer to item 5 in section 501.4.3 to determine applicability of this table)

	One or multiple power vent or direct vent appliances or no combustion appliancesA	One or multiple fan-assisted appliances and power vent or direct vent appliancesB	One atmospherically vented gas or oil appliance or one solid fuel applianceC	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliancesD
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor (cfm/sf)	0.25	0.15	0.10	0.05
b) conditioned floor area (sf)	_____	_____	_____	_____
(including unfinished basements)
Estimated House Infiltration (cfm): [1a x 1b]	_____	_____	_____	_____
or Alternative Calculation (by using blower door test)E
c) conversion factor	0.75	0.45	0.30	0.15
d) CFM50 value (from blower door test)	_____	_____	_____	_____
Estimated House Infiltration (cfm): [1c x 1d]	_____	_____	_____	_____
2. Exhaust Capacity
80% of exhaust rating = Exhaust Capacity (cfm):	_____	_____	_____	_____
(not applicable if recirculating system or if powered makeup air is electrically interlocked with exhaust)
3. Makeup Air Requirement
a) Exhaust Capacity (from above)	_____	_____	_____	_____
b) Estimated House Infiltration (from above)	_____	_____	_____	_____
Makeup Air Quantity (cfm): [3a - 3b]	_____	_____	_____	_____
(if value is negative, no makeup air is needed)
4. For Makeup Air Opening Sizing, refer to Table 501.4.2

1. Use this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.
2. Use this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.
3. Use this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.
4. Use this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliances.
5. As an alternative, the Estimated House Infiltration may be calculated by performing a blower door test and multiplying the conversion factor by the CFM50 value.

Table 501.4.3(3)
Procedure to Determine Makeup Air Quantity for Exhaust Appliances in Existing Dwellings
(Refer to item 6 in section 501.4.3 to determine applicability of this table)

	One or multiple power vent or direct vent appliances or no combustion appliancesA	One or multiple fan-assisted appliances and power vent or direct vent appliancesB	One atmospherically vented gas or oil appliance or one solid fuel applianceC	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliancesD
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor (cfm/sf)	0.25	0.15	0.10	0.05
b) conditioned floor area (sf)	_____	_____	_____	_____
(including unfinished basements)
Estimated House Infiltration (cfm): [1a x 1b]	_____	_____	_____	_____
or Alternative Calculation (by using blower door test)E
c) conversion factor	0.75	0.45	0.30	0.15
d) CFM50 value (from blower door test)	_____	_____	_____	_____
Estimated House Infiltration (cfm): [1c x 1d]	_____	_____	_____	_____
2. Exhaust Capacity
a) clothes dryer (cfm)	135	135	135	135
b) 80% of largest exhaust rating (cfm):	_____	_____	_____	_____
(not applicable if recirculating system or if powered makeup air is electrically interlocked and with exhaust)
c) 80% of next largest exhaust rating (cfm)	Not applicable	_____	_____	_____
(not applicable if recirculating system or if powered makeup air is electrically interlocked with exhaust)
Total Exhaust Capacity (cfm): [2a+2b+2c]	_____	_____	_____	_____
3. Makeup Air Requirement
a) Total Exhaust Capacity (from above)	_____	_____	_____	_____
b) Estimated House Infiltration (from above)	_____	_____	_____	_____
Makeup Air Quantity (cfm): [3a - 3b]	_____	_____	_____	_____
(if value is negative, no makeup air is needed)
4. For Makeup Air Opening Sizing, refer to Table 501.4.2

1. Use this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.
2. Use this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.
3. Use this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.
4. Use this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliances.
5. As an alternative, the Estimated House Infiltration may be calculated by performing a blower door test and multiplying the conversion factor by the CFM50 value.

The inlet to an exhaust system shall be located in the area of heaviest concentration of contaminants.

The bottom of an air inlet or exhaust opening in fuel-dispensing areas shall be located not more than 18 inches (457 mm) above the floor.

Equipment, appliance and system service rooms that house sources of odors, fumes, noxious gases, smoke, steam, dust, spray or other contaminants shall be designed and constructed so as to prevent spreading of such contaminants to other occupied parts of the building.

The mechanical exhaust of high concentrations of dust or hazardous vapors shall conform to the requirements of Section 510.

Type II dry cleaning systems shall be provided with a mechanical ventilation system that is designed to exhaust 1 cubic foot of air per minute for each square foot of floor area (1 cfm/ft²) [0.00508 m³/ (s • m²)] in dry cleaning rooms and in drying rooms. The ventilation system shall operate automatically when the dry cleaning equipment is in operation and shall have manual controls at an approved location.

Scrubbing tubs, scouring, brushing or spotting operations shall be located such that solvent vapors are captured and exhausted by the ventilating system.

Ventilation shall be provided for operations involving the application of materials containing flammable solvents in the course of construction, alteration or demolition of a structure.

Positive mechanical ventilation that provides not less than six complete air changes per hour shall be installed in limited spraying spaces. Such system shall meet the requirements of the International Fire Code for handling flammable vapors. Explosion venting is not required.

Mechanical ventilation of flammable vapor areas shall be provided in accordance with Sections 502.7.3.1 through 502.7.3.6.

Flammable vapor areas of dip tank operations shall be provided with mechanical ventilation adequate to prevent the dangerous accumulation of vapors. Required ventilation systems shall be so arranged that the failure of any ventilating fan will automatically stop the dipping conveyor system.

The flammable vapor area in spray-finishing operations involving electrostatic apparatus and devices shall be ventilated in accordance with Section 502.7.3.

Exhaust ventilation for powder-coating operations shall be sufficient to maintain the atmosphere below one-half of the minimum explosive concentration for the material being applied. Nondeposited, air-suspended powders shall be removed through exhaust ducts to the powder recovery system.

To prevent the accumulation of flammable vapors during floor resurfacing operations, mechanical ventilation at a minimum rate of 1 cfm/ft² [0.00508 m³/(s • m²)] of area being finished shall be provided. Such exhaust shall be by approved temporary or portable means. Vapors shall be exhausted to the outdoors.

The ventilation system for gas rooms, exhausted enclosures and gas cabinets for any quantity of hazardous material shall be designed to operate at a negative pressure in relation to the surrounding area. Highly toxic and toxic gases shall comply with Sections 502.9.7.1, 502.9.7.2 and 502.9.8.4.

Where closed systems for the use of hazardous materials in amounts exceeding the maximum allowable quantity per control area are designed to be opened as part of normal operations, ventilation shall be provided in accordance with Section 502.8.4.

Where corrosive materials in amounts exceeding the maximum allowable quantity per control area are dispensed or used, mechanical exhaust ventilation in accordance with Section 502.8.4 shall be provided.

Squirrel cage blowers shall not be used for exhausting hazardous fumes, vapors or gases in operating buildings and rooms for the manufacture, assembly or testing of explosives. Only nonferrous fan blades shall be used for fans located within the ductwork and through which hazardous materials are exhausted. Motors shall be located outside the duct.

Ventilation exhaust shall be provided for highly toxic and toxic liquids as required by Sections 502.9.6.1 and 502.9.6.2.

Ventilation exhaust shall be provided for highly toxic and toxic compressed gases in any quantity as required by Sections 502.9.7.1 and 502.9.7.2.

Ventilation exhaust shall be provided for highly toxic and toxic compressed gases in amounts exceeding the maximum allowable quantities per control area as required by Sections 502.9.8.1 through 502.9.8.6.

Ozone cabinets and ozone gas-generator rooms for systems having a maximum ozone-generating capacity of ¹/₂ pound (0.23 kg) or more over a 24-hour period shall be mechanically ventilated at a rate of not less than six air changes per hour. For cabinets, the average velocity of ventilation at makeup air openings with cabinet doors closed shall be not less than 200 feet per minute (1.02 m/s).

LP-gas distribution facilities shall be ventilated in accordance with NFPA 58.

Exhausted enclosures and gas cabinets for the indoor storage of silane gas in amounts exceeding the maximum allowable quantities per control area shall comply with Chapter 64 of the International Fire Code.

Exhaust ducts penetrating fire barriers constructed in accordance with Section 707 of the International Building Code or horizontal assemblies constructed in accordance with Section 711 of the International Building Code shall be contained in a shaft of equivalent fire-resistance-rated construction. Exhaust ducts shall not penetrate fire walls. Fire dampers shall not be installed in exhaust ducts.

Treatment systems for highly toxic and toxic gases shall comply with the International Fire Code.

Projectors equipped with an exhaust discharge shall be directly connected to a mechanical exhaust system. The exhaust system shall operate at an exhaust rate as indicated by the manufacturer's installation instructions.

Projectors without an exhaust connection shall have contaminants exhausted through a mechanical exhaust system. The exhaust rate for electric arc projectors shall be not less than 200 cubic feet per minute (cfm) (0.09 m³/s) per lamp. The exhaust rate for xenon projectors shall be not less than 300 cfm (0.14 m³/s) per lamp. Xenon projector exhaust shall be at a rate such that the exterior temperature of the lamp housing does not exceed 130°F (54°C). The lamp and projection room exhaust systems, whether combined or independent, shall not be interconnected with any other exhaust or return system within the building.

Repair garages used for the repair of hydrogen-fueled vehicles shall be provided with an approved exhaust ventilation system in accordance with this code and Chapter 6 of NFPA 2.

Each buffing machine shall be connected to a dust-collecting system that prevents the accumulation of the dust produced by the buffing process.

The passageway of dryer exhaust duct terminals shall be undiminished in size and shall provide an open area of not less than 12.5 square inches (8065 mm²).

Exhaust ducts shall have a smooth interior finish and shall be constructed of metal not less than 0.016 inch (0.4 mm) in thickness. The exhaust duct size shall be 4 inches (102 mm) nominal in diameter.

Transition ducts used to connect the dryer to the exhaust duct system shall be a single length that is listed and labeled in accordance with UL 2158A. Transition ducts shall be not greater than 8 feet (2438 mm) in length and shall not be concealed within construction.

The maximum allowable exhaust duct length shall be determined by one of the methods specified in Sections 504.8.4.1 through 504.8.4.3.

Where the exhaust duct equivalent length exceeds 35 feet (10 668 mm), the equivalent length of the exhaust duct shall be identified on a permanent label or tag. The label or tag shall be located within 6 feet (1829 mm) of the exhaust duct connection.

Ducts and plenums serving Type II hoods shall be constructed of rigid metallic materials. Duct construction, installation, bracing, and supports shall comply with Chapter 6. Ducts subject to positive pressure or conveying moisture-laden air, or both, and ducts conveying waste-heat-laden air shall be tested pursuant to section 506.4.1.1.

Exhaust outlets serving Type II hoods shall terminate in accordance with the hood manufacturer's installation instructions and shall comply with all of the following:

1. Exhaust outlets shall terminate not less than three feet (914 mm) in any direction from openings into the building.
2. Outlets shall terminate not less than ten feet (3,048 mm) from property lines or buildings on the same lot.
3. Outlets shall terminate not less than ten feet (3,048 mm) above grade.
4. Outlets that terminate above a roof shall terminate not less than 30 inches (762 mm) above the roof surface.
5. Outlets shall terminate not less than 30 inches (762 mm) from exterior vertical walls.
6. Outlets shall be protected against local weather conditions.
7. Outlets shall not be directed onto walkways.
8. Outlets shall meet the provisions for exterior wall opening protectives in accordance with the International Building Code.

Type I hood construction and installation shall comply with NFPA 96 and ASHRAE 154.

Type II hood construction and installation shall comply with this code and ASHRAE 154.

Equipment or machinery located inside buildings at lumber yards and woodworking facilities that generates or emits combustible dust shall be provided with an approved dust-collection and exhaust system installed in accordance with this section and the International Fire Code. Equipment and systems that are used to collect, process or convey combustible dusts shall be provided with an approved explosion-control system.

Equipment or machinery within a building that generates or emits combustible fibers shall be provided with an approved dust-collecting and exhaust system. Such systems shall comply with this code and the International Fire Code.

Systems conveying explosive or radioactive materials shall be prebalanced by duct sizing. Other systems shall be balanced by duct sizing with balancing devices, such as dampers. Dampers provided to balance airflow shall have securely fixed minimum-position blocking devices to prevent restricting the flow below the required volume or velocity.

The design of the system shall be such that the emissions are confined to the area in which they are generated by air currents, hoods or enclosures and shall be exhausted by a duct system to a safe location or treated by removing contaminants.

Hoods or enclosures shall be used where contaminants originate in a limited area of a space. The design of the hood or enclosure shall be such that air currents created by the exhaust systems will capture the contaminants and transport them directly to the exhaust duct.

The velocity and circulation of air in work areas shall be such that contaminants are captured by an airstream at the area where the emissions are generated and conveyed into a product-conveying duct system. Contaminated air from work areas where hazardous contaminants are generated shall be diluted below the thresholds specified in Section 510.2 with air that does not contain other hazardous contaminants.

Makeup air shall be provided at a rate approximately equal to the rate that air is exhausted by the hazardous exhaust system. Makeup air intakes shall be located in accordance with Section 401.4.

The minimum clearance between hoods and combustible construction shall be the clearance required by the duct system.

Hazardous exhaust duct systems shall extend directly to the exterior of the building and shall not extend into or through ducts and plenums.

Fire dampers and smoke dampers are prohibited in hazardous exhaust ducts.

Hazardous exhaust systems that penetrate a floor/ceiling assembly shall be enclosed in a fire-resistance-rated shaft constructed in accordance with the International Building Code.

Hazardous exhaust duct systems that penetrate fire-resistance-rated wall assemblies shall be enclosed in fire-resistance-rated construction from the point of penetration to the outlet terminal, except where the interior of the duct is equipped with an approved automatic fire suppression system. Ducts shall be enclosed in accordance with the International Building Code requirements for shaft construction and such enclosure shall have a minimum fire-resistance rating of not less than the highest fire-resistance-rated wall assembly penetrated.

Ducts shall not penetrate a fire wall.

Ducts conveying combustible dust as part of a dust collection system shall be equipped with cleanouts that are provided with approved access, predesigned to be disassembled for cleaning, or engineered for automatic cleanouts. Where provided, cleanouts shall be located at the base of each vertical duct riser and at intervals not exceeding 20 feet (6096 mm) in horizontal sections of duct.

Ducts shall be made tight with lap joints having a minimum lap of 1 inch (25 mm). Joints used in ANSI/SMACNA Round Industrial Duct Construction Standards and ANSI/SMACNA Rectangular Industrial Duct Construction Standards are also acceptable.

Systems exhausting potentially explosive mixtures shall be protected with an approved explosion relief system or by an approved explosion prevention system designed and installed in accordance with NFPA 69. An explosion relief system shall be designed to minimize the structural and mechanical damage resulting from an explosion or deflagration within the exhaust system. An explosion prevention system shall be designed to prevent an explosion or deflagration from occurring.

Discharge piping shall conform to the requirements for ducts, including clearances required for high-heat appliances, as contained in this code. A delivery pipe from a cyclone collector shall not convey refuse directly into the firebox of a boiler, furnace, dutch oven, refuse burner, incinerator or other appliance.

An exhaust system shall discharge to the outside of the building either directly by flue or indirectly through the bin or vault into which the system discharges except where the contaminants have been removed. Exhaust system discharge shall be permitted to be recirculated provided that the solid particulate has been removed at a minimum efficiency of 99.9 percent at 10 microns (10.01 mm), vapor concentrations are less than 25 percent of the LFL, and approved equipment is used to monitor the vapor concentration.

The outlet of an open-air exhaust terminal shall be protected with an approved metal or other noncombustible screen to prevent the entry of sparks.

A safety or explosion relief vent shall be provided on all systems that convey combustible refuse or stock of an explosive nature, in accordance with the requirements of the International Building Code.

The system shall be designed such that the maximum probable normal or reverse stack effects will not adversely interfere with the system's capabilities. In determining the maximum probable stack effects, altitude, elevation, weather history and interior temperatures shall be used.

Buoyancy and expansion caused by the design fire in accordance with Section 513.9 shall be analyzed. The system shall be designed such that these effects do not adversely interfere with its capabilities.

The design shall consider the adverse effects of wind. Such consideration shall be consistent with the wind-loading provisions of the International Building Code.

The design shall consider the effects of the heating, ventilating and air-conditioning (HVAC) systems on both smoke and fire transport. The analysis shall include all permutations of systems' status. The design shall consider the effects of fire on the HVAC systems.

The design shall consider the effects of low temperatures on systems, property and occupants. Air inlets and exhausts shall be located so as to prevent snow or ice blockage.

All portions of active or engineered smoke control systems shall be capable of continued operation after detection of the fire event for a period of not less than either 20 minutes or 1.5 times the calculated egress time, whichever is greater.

The design shall consider the interaction effects of the operation of multiple smoke control systems for all design scenarios.

Total leakage area of the barrier is the product of the smoke barrier gross area times the allowable leakage area ratio, plus the area of other openings such as gaps around doors and operable windows.

Compliance with the maximum total leakage area shall be determined by achieving the minimum air pressure difference across the barrier with the system in the smoke control mode for mechanical smoke control systems utilizing the pressurization method. Compliance with the maximum total leakage area of passive smoke control systems shall be verified through methods such as door fan testing or other methods, as approved by the fire code official.

Where stairways or elevator hoistways are pressurized, such pressurization systems shall comply with Section 513 as smoke control systems, in addition to the requirements of Sections 909.20 of the International Building Code and 909.21 of the International Fire Code.

This method shall not be employed where either the quantity of air or the velocity of the airflow will adversely affect other portions of the smoke control system, unduly intensify the fire, disrupt plume dynamics or interfere with exiting. Airflow toward the fire shall not exceed 200 feet per minute (1.02 m/s). Where the calculated airflow exceeds this limit, the airflow method shall not be used.

The height of the lowest horizontal surface of the accumulating smoke layer shall be maintained not less than 6 feet (1829 mm) above any walking surface that forms a portion of a required egress system within the smoke zone.

The engineering analysis shall include the characteristics of the fuel, fuel load, effects included by the fire and whether the fire is likely to be steady or unsteady.

Determination of the design fire shall include consideration of the type of fuel, fuel spacing and configuration.

The analysis shall make use of the best available data from approved sources and shall not be based on excessively stringent limitations of combustible material.

A documented engineering analysis shall be provided for conditions that assume fire growth is halted at the time of sprinkler activation.

Equipment shall be located so as to not expose uninvolved portions of the building to an additional fire hazard. Outdoor air inlets shall be located so as to minimize the potential for introducing smoke or flame into the building. Exhaust outlets shall be so located as to minimize reintroduction of smoke into the building and to limit exposure of the building or adjacent buildings to an additional fire hazard.

Automatic dampers, regardless of the purpose for which they are installed within the smoke control system, shall be listed and conform to the requirements of approved recognized standards.

In addition to other requirements, belt-driven fans shall have 1.5 times the number of belts required for the design duty with the minimum number of belts being two. Fans shall be selected for stable performance based on normal temperature and, where applicable, elevated temperature. Calculations and manufacturer's fan curves shall be part of the documentation procedures. Fans shall be supported and restrained by noncombustible devices in accordance with the structural design requirements of the International Building Code. Motors driving fans shall not be operating beyond their nameplate horsepower (kilowatts) as determined from measurement of actual current draw. Motors driving fans shall have a minimum service factor of 1.15.

The standby power source and its transfer switches shall be in a room separate from the normal power transformers and switch gear and ventilated directly to and from the exterior. The room shall be enclosed with not less than 1-hour fire-resistance-rated fire barriers constructed in accordance with Section 707 of the International Building Code or horizontal assemblies constructed in accordance with Section 711 of the International Building Code, or both.

Elements of the smoke management system relying on volatile memories or the like shall be supplied with uninterruptible power sources of sufficient duration to span 15-minute primary power interruption. Elements of the smoke management system susceptible to power surges shall be suitably protected by conditioners, suppressors or other approved means.

In addition to meeting the requirements of NFPA 70, all wiring, regardless of voltage, shall be fully enclosed within continuous raceways.

Smoke control systems shall be activated in accordance with the International Building Code or the International Fire Code.

Where complete automatic control is required or used, the automatic control sequences shall be initiated from an appropriately zoned automatic sprinkler system complying with Section 903.3.1.1 of the International Fire Code, from manual controls provided with ready access for the fire department, and any smoke detectors required by engineering analysis.

Control tubing serving other than smoke control functions shall be isolated by automatic isolation valves or shall be an independent system.

Control-air tubing shall be tested at three times the operating pressure for not less than 30 minutes without any noticeable loss in gauge pressure prior to final connection to devices.