Wall-mounted bathroom exhaust fan

[BayPointArchitect]

Applicable Codes: 2009 IBC and IMC

Type of Occupancy: R2

New apartment building

Type of Construction: VA/Sprinkled

Question:

What exception is there for having a fire damper for the bathroom exhaust while that grill is located within the wall rather than the ceiling. There is a rigid duct from the exhaust fan (wall-mounted) up to the floor ceiling interstitial space. But as it starts to weave through the floor truss system, it transitions to a flex duct (not 24 or 26 gauge) to the exterior face of the building.

What exception is there for having a fire damper?

thank you!

 

[north star]

& = = = &

See this link to Ch. 6 [ `09 IMC ], Section 607.6.1 - Thru penetrations:

http://publicecodes.cyberregs.com/icod/imc/2009/icod_imc_2009_6_par108.htm



= & & & =

 

[Builder Bob]

717.5.4 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. Corridor walls in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 and the duct is protected as a through penetration in accordance with Section 714.

2. Tenant partitions in covered and open mall buildings where the walls are not required by provisions elsewhere in the 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 the International Mechanical Code and the duct penetrating the wall complies with all of the following requirements:

3.1. The duct shall not exceed 100 square inches (0.06 m2).

3.2. The duct shall be constructed of steel a minimum of 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 11/2-inch by 11/2-inch by 0.060-inch (38 mm by 38 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 mineral wool batting on all sides.

4. Such walls are penetrated by ducted HVAC systems, have a required fire-resistance rating of 1 hour or less, and are in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2. 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 No. 26 gage thickness and shall be continuous from the air-handling appliance or equipment to the air outlet and inlet terminals.

 

[BayPointArchitect]

That is exactly what I needed. In this case, we can leave the bathroom exhaust vents without a fire damper but it is unlikely that the 4 inch diameter flex duct in the ceiling will need to be replaced with a thicker 26 gauge rigid duct.

 

[Builder Bob]

Make sure that the exhaust vent is not in the common rated corridor wall.... you may have to offset into an interior non-rated wall if it is in the common corridor wall.