N.Y.C. Admin. Code § MC 607: Section MC 607: Ducts and Air Transfer Openings

607.1 General.

The provisions of this section shall govern the protection of duct penetrations and air transfer openings in fire-resistance-rated assemblies required to be protected.

607.1.1 Ducts and air transfer openings.

Ducts transitioning horizontally between shafts shall comply with one of the following:

1. The horizontal enclosure between shafts shall match the required rating of the shafts.

2. Fire-resistive duct assemblies shall be provided in accordance with Section 604. The duct assembly shall comply with all of the following:

2.1. Ducts shall not be within the scope of Sections 502.10, 504, 506.3, 510, or 511; and

2.2. Ducts shall not be lined with nor convey combustible materials; and

2.3. Ducts shall not be constructed of materials that are sensitive to thermal shock.

3. The horizontal offset duct shall be provided with combination fire-smoke dampers at the penetration of each shaft. The duct system shall comply with all of the following:

3.1. Ducts shall not be within the scope of Sections 502.10, 504, 506.3, 510, or 511; and

3.2. The duct system shall be a type permitted to include dampers; and

3.3. Protection of penetrations of the shaft enclosure shall not utilize exceptions requiring continuous air movement.

607.1.2 Ducts that penetrate fire-resistance-rated assemblies without dampers.

Ducts that penetrate fire-resistance-rated assemblies and are not required by this section to have dampers shall comply with the requirements of Sections 714.2 through 714.3.3 of the New York City Building Code. Ducts that penetrate horizontal assemblies not required to be contained within a shaft and not required by this section to have dampers shall comply with the requirements of Sections 714.4 of the New York City Building Code.

607.1.2.1 Ducts that penetrate nonfire-resistance-rated assemblies.

The space around a duct penetrating a nonfire-resistance-rated floor assembly shall comply with Section 717.6.3 of the New York City Building Code.

607.2 Installation.

Fire dampers, smoke dampers, combination fire/smoke dampers and ceiling radiation dampers located within air distribution and smoke control systems shall be installed in accordance with the requirements of this section, and the manufacturer's instructions and listing.

607.2.1 Smoke control system.

Where the installation of a fire damper will interfere with the operation of a required smoke control system in accordance with Section 909 of the New York City Building Code, approved alternative protection shall be used. Where mechanical systems including ducts and dampers used for normal building ventilation serve as part of the smoke control system, the expected performance of these systems in smoke control mode shall be addressed in the rational analysis required by Section 909.4 of the New York City Building Code.

607.2.1.1 Remote operation.

Combination fire and smoke dampers shall be operable by remote controls where necessary for smoke removal. Such dampers shall have provisions that allow them to reclose automatically upon reaching the damper's maximum degradation test temperature in accordance with UL 555S.

607.2.2 Hazardous exhaust ducts.

Fire dampers for hazardous exhaust duct systems shall comply with Section 510.

607.2.3 Supply air systems.

Smoke dampers listed for use in air distribution systems shall be installed both upstream and downstream of filters and ahead of any branch connections in supply air-handling apparatus and systems having a capacity equal to or greater than 15,000 cfm (7.1 m

3

/s).

Exceptions:

1. Where the air-handling unit is located on the floor that it serves and serves only that floor.

2. Where the air-handling unit is located on the roof and serves only the floor immediately below the roof.

607.3 Damper testing, ratings and actuation.

Damper testing, ratings and actuation shall be in accordance with Sections 607.3.1 through 607.3.3.

607.3.1 Damper testing.

Dampers shall be listed and bear the label of an approved testing agency indicating compliance with the standards in this section. Fire dampers shall comply with the requirements of UL 555. Only fire dampers and ceiling radiation dampers labeled for use in dynamic systems shall be installed in heating, ventilating and air-conditioning systems designed to operate with fans on during a fire. Smoke dampers shall comply with the requirements of UL 555S. Combination fire/smoke dampers shall comply with the requirements of both UL 555 and UL 555S. Ceiling radiation dampers shall comply with the requirements of UL 555C-Ceiling Dampers.

607.3.2 Damper rating.

Damper ratings shall be in accordance with Sections 607.3.2.1 through 607.3.2.3.

607.3.2.1 Fire damper ratings.

Fire dampers shall have the minimum fire protection rating specified in Table 607.3.2.1 for the type of penetration.

Table 607.3.2.1 Fire Damper Rating

Type of Penetration

Minimum Damper Rating (hour)

Less than 3-hour fire-resistance-rated assemblies

1 1/2

3-hour or greater fire-resistance-rated assemblies

3

607.3.2.2 Smoke damper ratings.

Smoke damper leakage ratings shall be Class I or II. Elevated temperature ratings shall be not less than 250°F (121.1°C).

607.3.2.3 Combination fire/smoke damper ratings.

Combination fire/smoke dampers shall have the minimum fire protection rating specified for fire dampers in Table 607.3.2.1 for the type of penetration and shall have a minimum smoke damper rating as specified in Section 607.3.2.2.

607.3.3 Damper actuation.

Damper actuation shall be in accordance with Sections 607.3.3.1 through 607.3.3.4 as applicable.

607.3.3.1 Fire damper actuation device.

The fire damper actuation device shall meet one of the following requirements:

1. The operating temperature shall be approximately 50°F (10°C) above the normal temperature within the duct system, but not less than 160°F (71.1°C).

2. The operating temperature shall be not more than 350°F (176.7°C) where located in a smoke control system complying with Section 909 of the New York City Building Code.

607.3.3.2 Smoke damper actuation.

The smoke damper shall close upon actuation of a listed smoke detector or detectors installed in accordance with Section 606 of this code and Section 907.3 of the New York City Building Code and one of the following methods, as applicable:

1. Where a smoke damper is installed within a duct, a smoke detector shall be installed inside the duct or outside the duct with sampling tubes protruding into the duct. The detector or tubes within the duct shall be within 5 feet (1524 mm) of the damper. Air outlets and inlets shall not be located between the detector or tubes and the damper. The detector shall be listed for the air velocity, temperature and humidity anticipated at the point where it is installed. Other than in mechanical smoke control systems, dampers shall be closed upon fan shutdown where local smoke detectors require a minimum velocity to operate.

Exception: Duct smoke detectors will not be required at each smoke or combination fire smoke damper provided:

1. The supply fan shall shut down and all the smoke and combination fire smoke dampers associated with the supply system automatically close upon actuation of any automatic alarm initiating device on the floor(s).

2. Nonducted return air systems shall have a smoke detector located within 5 feet (1.5 m) upstream of each return air or transfer opening in a fire barrier rated 2-hour or greater.

3. Ducted return air systems shall have a duct smoke detector located within 5 feet (1.5 m) of a smoke damper; additional smoke detectors are not required at smoke and combination fire smoke dampers located downstream where there are no additional return air inlets.

2. Where a smoke damper is installed above smoke barrier doors in a smoke barrier, a spot-type detector shall be installed on either side of the smoke barrier door opening. The detector shall be listed for releasing service if used for direct interface with the damper.

3. Where a smoke damper is installed within an unducted opening in a wall, a spot-type detector shall be installed within 5 feet (1524 mm) horizontally of the damper. The detector shall be listed for releasing service if used for direct interface with the damper.

4. Where a smoke damper is installed in a corridor wall or ceiling, the damper shall be permitted to be controlled by a smoke detection system installed in the corridor.

5. Where a smoke detection system is installed in all areas served by the duct in which the damper will be located, the smoke dampers shall be permitted to be controlled by the smoke detection system.

6. Smoke dampers that are part of an engineered smoke control system shall be capable of being positioned manually from a command station. Such positioning devices shall be provided for supply and return/exhaust dampers grouped by floor and by type. Damper switch positions shall indicate whether the related dampers are commanded to be either open or closed. Smoke damper positioning switches shall be located at the Fire Command Station, or in a Mechanical Control Center in buildings without a Fire Command Station.

607.3.3.3 Combination fire/smoke damper actuation.

Combination fire/smoke damper actuation shall be in accordance with Sections 607.3.3.1 and 607.3.3.2. Combination fire/smoke dampers installed in smoke control system shaft penetrations shall not be activated by local area smoke detection unless it is secondary to the smoke management system controls.

607.3.3.4 Ceiling radiation damper actuation.

The operating temperature of a ceiling radiation damper actuation device shall be 50°F (10°C) above the normal temperature within the duct system, but not less than 160°F (71.1°C).

607.4 Access and identification.

Fire and smoke dampers shall be provided with an approved means of access, large enough to permit inspection and maintenance of the damper and its operating parts. The access shall not affect the integrity of fire-resistance-rated assemblies. The access openings shall not reduce the fire-resistance rating of the assembly. Access points shall be permanently identified on the exterior by a label having letters not less than 0.5 inch (12.7 mm) in height reading: FIRE/SMOKE DAMPER, SMOKE DAMPER or FIRE DAMPER, followed by an identification marking that is individual and unique to the damper accessed. Access doors in ducts shall be tight fitting and suitable for the required duct construction.

607.5 Where required.

Fire dampers, smoke dampers, and combination fire/smoke dampers shall be provided at the locations prescribed in Sections 607.5.1 through 607.5.7. Where an assembly is required to have both fire dampers and smoke dampers, combination fire/smoke dampers or a fire damper and smoke damper shall be provided.

Exceptions:

1. Ducts 20 square inches (12 903 mm

2

) or less passing through fire-resistance-rated assemblies other than fire walls shall not require fire dampers or smoke dampers.

2. Smoke dampers shall not be required to be located within a prescribed distance of a fire-rated enclosure and where isolation smoke dampers are used in air-handling equipment.

607.5.1 Fire walls.

Ducts and air transfer openings permitted in firewalls in accordance with Section 706.11 of the New York City Building Code shall be protected with listed fire dampers and smoke dampers installed in accordance with their listing.

Exception: Smoke dampers shall not be required in ducts where the air continues to move and the air-handling system installed is arranged to prevent recirculation of exhaust or return air under fire emergency conditions or loss of normal power by provision of standby power in accordance with Chapter 27 of the New York City Building Code.

607.5.1.1 Horizontal exits.

A listed smoke damper designed to resist the passage of smoke shall be provided at each point that a duct or air transfer opening penetrates a fire wall that serves as a horizontal exit.

Exception: Smoke dampers shall not be required in ducts where the air continues to move and the air-handling system installed is arranged to prevent recirculation of exhaust or return air under fire emergency conditions or loss of normal power by provision of standby power in accordance with Chapter 27 of the New York City Building Code.

607.5.2 Fire barriers.

Ducts and air transfer openings that penetrate fire barriers shall be protected with listed fire dampers installed in accordance with their listing. Ducts and air transfer openings shall not penetrate enclosures for interior exit stairways and ramps and exit passageways except as permitted by Sections 1023.5 and 1024.6, respectively, of the New York City Building Code. In addition, smoke dampers shall be installed in penetrations of public corridor and horizontal exit walls in accordance with Section 607.5.2.1.

Exceptions: Fire dampers are not required at penetrations of fire barriers where any of the following apply:

1. Penetrations are tested in accordance with ASTM E 119 or UL 263 as part of the fire-resistance-rated assembly.

2. Ducts are used as part of an engineered smoke control system in accordance with Section 513 of this Code and Section 909 of the New York City Building Code and where the fire damper would interfere with the operation of the smoke control system.

3. Such walls are penetrated by ducted HVAC systems, have a required fire-resistance rating of 1 hour or less, are in areas other than Group H and are in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 of the New York City Building Code. For the purposes of this exception, a ducted HVAC system shall be a duct system for the structure's HVAC system. Such a duct system shall be constructed of sheet metal not less than 26 gage (0.0217 inch) (0.55 mm) thickness and shall be continuous from the air-handling appliance or equipment to the air outlet and inlet terminals.

607.5.2.1 Horizontal exits.

A listed smoke damper designed to resist the passage of smoke shall be provided at each point that a duct or air transfer opening penetrates a fire barrier that serves as a horizontal exit.

Exception: Smoke dampers shall not be required in ducts where the air continues to move and the air-handling system installed is arranged to prevent recirculation of exhaust or return air under fire emergency conditions.

607.5.2.2 Public corridors.

A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a public corridor wall constructed as a fire barrier.

Exceptions:

1. Smoke dampers are not required where the building is equipped throughout with an approved smoke control system in accordance with Section 909 of the New York City Building Code, and smoke dampers are not necessary for the operation and control of the system.

2. Smoke dampers are not required in corridor penetrations where the duct is constructed of steel not less than 0.019 inch (0.48 mm) in thickness and there are no openings serving the corridor.

3. Smoke dampers are not required in corridor penetrations in Group R-2 buildings and public corridors serving R-2 spaces in mixed use buildings.

4. Smoke dampers shall not be required in ducts where the air continues to move and the air-handling system installed is arranged to prevent recirculation of exhaust or return air under fire emergency conditions or loss of normal power by provision of standby power in accordance with Chapter 27 of the New York City Building Code.

607.5.3 Fire partitions.

Ducts and air transfer openings that penetrate fire partitions shall be protected with listed fire dampers installed in accordance with their listing.

Exceptions: In occupancies other than Group H, fire dampers are not required where any of the following apply:

1. The partitions are tenant separation and corridor walls in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 of the New York City Building Code and the duct is protected as a through penetration in accordance with Section 714 of the New York City Building Code.

2. The partitions are tenant partitions in covered and open mall buildings where the walls are not required by provisions elsewhere in the New York City Building Code to extend to the underside of the floor or roof sheathing, slab or deck above.

3. The duct system is constructed of approved materials in accordance with this code and the duct penetrating the wall complies with all of the following minimum requirements:

3.1. The duct shall not exceed 100 square inches (0.06 m

2

).

3.2. The duct shall be constructed of steel not less than 0.0217 inch (0.55 mm) in thickness.

3.3. The duct shall not have openings that communicate the corridor with adjacent spaces or rooms.

3.4. The duct shall be installed above a ceiling.

3.5. The duct shall not terminate at a wall register in the fire-resistance-rated wall.

3.6. A minimum 12-inch-long (305 mm) by 0.060-inch-thick (1.52 mm) steel sleeve shall be centered in each duct opening. The sleeve shall be secured to both sides of the wall and all four sides of the sleeve with minimum 1 1/2-inch by 1 1/2-inch by 0.060-inch (38.1 mm by 38.1 mm by 1.52 mm) steel retaining angles. The retaining angles shall be secured to the sleeve and the wall with No. 10 (M5) screws. The annular space between the steel sleeve and the wall opening shall be filled with rock (mineral) wool batting or approved equivalent on all sides.

4. Such partitions are penetrated by ducted HVAC systems, have a required fire-resistance rating of 1 hour or less, and are in areas of other than Group H and are in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 of the New York City Building Code. For the purposes of this exception, a ducted HVAC system shall be a duct system for conveying supply, return or exhaust air as part of the structure's HVAC system. Such a duct system shall be constructed of sheet steel not less than 26 gage in thickness and shall be continuous from the air-handling appliance or equipment to the air outlet and inlet terminals.

607.5.4 Smoke barriers.

A listed smoke damper designed to resist the passage of smoke shall be provided at each point where a duct or an air transfer opening penetrates a smoke barrier wall enclosure required to have smoke and draft control doors in accordance with the New York City Building Code. Smoke dampers and smoke damper actuation methods shall comply with Section 607.5.4.1.

Exceptions:

1. Smoke dampers are not required in smoke barrier penetrations where the openings in ducts are limited to a single smoke compartment and the ducts are constructed of steel.

2. Smoke dampers are not required in ducts where the air continues to move and the air-handling system installed is arranged to prevent recirculation of exhaust or return air under fire emergency conditions.

607.5.4.1 Smoke damper.

The smoke damper shall close upon actuation of a listed smoke detector or detectors installed in accordance with the New York City Building Code and Section 607.3.3.2.

607.5.5 Shaft enclosures.

Ducts and air transfer openings shall not penetrate a shaft serving as an exit enclosure except as permitted by Section 1022.4 of the New York City Building Code. Shaft enclosures that are permitted to be penetrated by ducts and air transfer openings shall be protected with approved fire and smoke dampers installed in accordance with their listing.

Exceptions:

1. Fire dampers are not required at penetrations of shafts where any of the following apply:

1.1. In buildings equipped throughout with an automatic sprinkler system in accordance with Chapter 9 of the New York City Building Code, where steel exhaust subducts have a minimum thickness of 0.0187 inch (0.4712 mm) (No. 26 gage) and extend not less than 22 inches (558.8 mm) vertically in exhaust shafts, provided that there is a continuous airflow upward to the outdoors whenever the building is occupied.

1.2. Penetrations are tested in accordance with ASTM E 119 or UL 263 as part of the fire-resistance-rated assembly.

1.3. Ducts are used as part of an engineered smoke control system designed and installed in accordance with Section 909 of the New York City Building Code, and where the fire damper will interfere with the operation of the smoke control system.

1.4. The penetrations are in parking garage exhaust or supply shafts that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction.

2. Smoke dampers are not required in exhaust ducts or shafts where the exhaust fan is maintained in operation whenever the building is occupied, in bathrooms and toilet room exhausts.

3. Smoke dampers are not required at penetrations of exhaust or supply shafts in parking garages that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction.

4. Smoke dampers are not required at penetrations of shafts where ducts are used as part of an engineered mechanical smoke control system designed in accordance with Section 909 of the New York City Building Code and where the smoke damper will interfere with the operation of the smoke control system.

5. Fire dampers and/or smoke dampers are not required at a shaft where the shaft is acting as an extension of the mechanical equipment room that it serves and the shaft and mechanical equipment room maintain fire and smoke separation required by the greater of the two spaces from the occupied portions of the building and meet the requirements of Sections 713.11 and 713.12 of the New York City Building Code.

6. Smoke dampers are not required to be located within a prescribed distance of a fire-rated enclosure within which the air handling equipment is located and where isolation smoke dampers are used in air-handling equipment. See Section 607.2.3 for additional requirements.

7. Smoke dampers are not required in ducts where the air continues to move and the air-handling system installed is arranged to prevent recirculation of exhaust or return air during a fire emergency condition. Such fans shall be provided with standby power in accordance with Chapter 27 of the New York City Building Code.

607.5.5.1 Enclosure at the bottom.

Shaft enclosures that do not extend to the bottom of the building or structure shall be protected in accordance with Section 713.11 of the New York City Building Code.

607.5.5.2 Limitations.

Shafts that constitute air ducts or that enclose air ducts used for the movement of environmental air shall not enclose:

1. Exhaust ducts used for the removal of smoke and grease-laden vapors from cooking equipment;

2. Ducts used for removal of flammable vapors;

3. Ducts used for moving, conveying, or transporting stock, vapor or dust;

4. Ducts used for the removal of nonflammable corrosive fumes and vapors; 5. Refuse and linen chutes; or

6. Piping.

Exception: Shafts that constitute air ducts or that enclose air ducts used for the movement of environmental air may enclose noncombustible piping conveying water or other nonhazardous or nontoxic materials.

607.5.6 Exterior walls.

Ducts and air transfer openings in fire-resistance-rated exterior walls required to have protected openings in accordance with Section 705.10 of the New York City Building Code shall be protected with listed fire dampers installed in accordance with their listing.

607.5.6.1 Outdoor air intake openings.

An outdoor air intake opening with gross area of more than 144 square inches (92 903 mm

2

) shall be provided with fire dampers and smoke dampers, or combined fire and smoke dampers when such opening is located as follows (intake and exhaust separation requirements of Chapters 4 and 5 shall also be maintained):

1. Less than 30 feet (9144 mm) above grade.

2. Less than 30 feet (9144 mm) in any direction from any opening in another building.

3. Less than 15 feet (4572 mm) from a lot line.

4. Less than 50 feet (15 240 mm) above and less than 50 feet (15 240 mm) in any direction from a roof constructed of combustible material or a building in which the exterior walls are constructed wholly or partly of wood.

Exceptions:

1. Smoke dampers shall not be required for outdoor air intake openings of systems greater than 15,000 cfm (7.1 m

3

/s) which are provided with smoke dampers in accordance with Chapter 6 and arranged so as to not introduce smoke into the building or space in which the equipment is located.

2. A damper is not required where the combustion air intake duct, boiler room, and combustion air intake louver for such boiler room are enclosed with construction having a fire-resistance rating not less than the rating of the exterior wall, boiler room and any intervening space.

607.5.7 Smoke partitions.

A listed smoke damper designed to resist the passage of smoke shall be provided at each point where an air transfer opening penetrates a smoke partition. Smoke dampers and smoke damper actuation methods shall comply with Section 607.3.3.2.

Exceptions:

1. Where the installation of a smoke damper will interfere with the operation of a required smoke control system in accordance with Section 513, approved alternate protection shall be used.

2. Smoke dampers shall not be required in ducts where the air continues to move and the air-handling system installed is arranged to prevent recirculation of exhaust or return air under fire emergency conditions.

607.6 Horizontal assemblies.

Penetrations by air ducts of a floor, floor/ceiling assembly or the ceiling membrane of a roof/ceiling assembly shall be protected by a shaft enclosure that complies with the New York City Building Code or shall comply with this section.

607.6.1 Through penetrations.

In occupancies other than Groups I-2 and I-3, a duct and air transfer opening system constructed of approved materials in accordance with this code that penetrates a fire-resistance-rated floor/ceiling assembly that connects not more than two stories is permitted without shaft enclosure protection provided that a listed fire damper is installed at the floor line and the penetration is firestopped or the duct is protected in accordance with Section 714.4 of the New York City Building Code. For air transfer openings, see Item 6, Section 712.1.9 of the New York City Building Code.

Exception: A duct serving a dwelling unit is permitted to penetrate three floors or less without a fire damper at each floor provided such duct meets all of the following requirements.

1. The duct is contained and located within the cavity of a wall and is constructed of steel having a minimum thickness of 0.0187 inch (0.4712 mm) (No. 26 gage).

2. The duct opens into only one dwelling or sleeping unit and the duct system is continuous from the unit to the exterior of the building.

3. The duct does not exceed a 5 inch (127 mm) nominal diameter and the total area of such ducts does not exceed 100 square inches (64 516 mm

2

) for any 100 square feet (9.3 m

2

) of the floor area.

4. The annular space around the duct is protected with materials that prevent the passage of flame and hot gases sufficient to ignite cotton waste where subjected to ASTM E 119 or UL 263 time-temperature conditions under a minimum positive pressure differential of 0.01 inch (2.49 Pa) of water at the location of the penetration for the time period equivalent to the fire-resistance rating of the construction penetrated.

5. Grille openings located in a ceiling of a fire-resistance-rated floor/ceiling or roof/ceiling assembly are protected with a listed ceiling radiation damper installed in accordance with Section 607.6.2.1.

607.6.2 Membrane penetrations.

Ducts and air transfer openings constructed of approved materials, in accordance with Section 603, that penetrate the ceiling membrane of a fire-resistance-rated floor/ceiling or roof/ceiling assembly shall be protected with one of the following:

1. A shaft enclosure in accordance with Section 713 of the New York City Building Code.

2. A listed ceiling radiation damper and firestopping installed at the ceiling line where a duct penetrates the ceiling of a fire-resistance-rated floor/ceiling or roof/ceiling assembly.

3. A listed ceiling radiation damper and firestopping installed at the ceiling line where a diffuser with no duct attached penetrates the ceiling of a fire-resistance-rated floor/ceiling or roof/ceiling assembly.

607.6.2.1 Ceiling radiation dampers.

Ceiling radiation dampers shall be tested in accordance with Section 607.3.1. Ceiling radiation dampers shall be installed in accordance with the details listed in the fire-resistance-rated assembly and the manufacturer's instructions and listing. Ceiling radiation dampers are not required where any of the following apply:

1. Tests in accordance with ASTM E 119 or UL 263 have shown that ceiling radiation dampers are not necessary to maintain the fire-resistance rating of the assembly.

2. Where exhaust duct penetrations are protected in accordance with Section 714.4.2 of the New York City Building Code, are located within the cavity of a wall, and do not pass through another dwelling unit or tenant space.

3. Where duct and air transfer openings are protected with a duct outlet protection system tested as part of a fire-resistance-rated assembly in accordance with ASTM E 119 or UL 263 and the building is protected throughout with an automatic sprinkler system in accordance with Chapter 9 of the New York City Building Code.

607.6.3 Nonfire-resistance-rated floor assemblies.

Duct systems constructed of approved materials in accordance with Section 603 that penetrate nonfire-resistance-rated floor assemblies shall be protected by any of the following methods:

1. A shaft enclosure in accordance with Section 713 of the New York City Building Code.

2. The duct connects not more than two stories, and the annular space around the penetrating duct is protected with an approved noncombustible material that resists the free passage of flame and the products of combustion.

3. In floor assemblies composed of noncombustible materials, a shaft shall not be required where the duct connects not more than three stories, the annular space around the penetrating duct is protected with an approved noncombustible material that resists the free passage of flame and the products of combustion and a fire damper is installed at each floor line.

Exception: Fire dampers are not required in ducts within individual residential dwelling units.

607.7 Flexible ducts and air connectors.

Flexible ducts and air connectors shall not pass through any fire-resistance-rated assembly. Flexible air connectors shall not pass through any wall, floor or ceiling.