Clothes dryer exhaust duct- fire dampers

[Plumb-bob]

I cannot find any exemptions or special rules for where a clothes dryer exhaust duct penetrates a fire rated assembly. I assume a fire damper would be required at this location.


However, the installation of a damper in this duct would 1) cause lint buildup, and 2) the fusible link may not be compatible with the heat generated by the dryer.


I believe American codes exempt fire dampers from dryer ducts for these reasons.


Any comments or experiences to share?

 

[redeyedfly]

I don't know about Canada but the IBC has different rules for different types of fire rated assemblies. Just because it's penetrating a fire rated assy doesn't automatically require a damper (smoke or fire or both).

 

[Steve French]

I'm not familiar with the BCBC, but the NBC does have an applicable exemption part 9 for dryer exhaust ducts penetration ceiling assemblies with a FRR of 1-hr or less. Check out 9.10.5.1.(3) --> D-2.3.10. Ceiling Membrane Openings – Combustible Construction. Alternatively, you could cite 9.10.9.6.(1)(b) and make sure its galv duct throughout tightly fitted at the point of penetration, assuming you think it should be permitted in a situation where the requirements from Appendix D can't be met - e.g. penetrating a rated wall.

Part 3 likely has an equivalent, I just can't recall exactly where.

 

[Gregg Harris]

I cannot find any exemptions or special rules for where a clothes dryer exhaust duct penetrates a fire rated assembly. I assume a fire damper would be required at this location.


However, the installation of a damper in this duct would 1) cause lint buildup, and 2) the fusible link may not be compatible with the heat generated by the dryer.


I believe American codes exempt fire dampers from dryer ducts for these reasons.


Any comments or experiences to share?

Look at IMC 504.2 for dryer exhaust, and IBC both state dampers, sensors, etc, are prohibited for the reasons you stated.

 

[mtlogcabin]

Do the Canadian codes have anything similar to this
International Mechanical Code

504.2​

Where a clothes dryer exhaust duct penetrates a wall or ceiling membrane, the annular space shall be sealed with noncombustible material, approved fire caulking or a noncombustible dryer exhaust duct wall receptacle. Ducts that exhaust clothes dryers shall not penetrate or be located within any fireblocking, draft-stopping or any wall, floor/ceiling or other assembly required by the International Building Code to be fire-resistance rated, unless such duct is constructed of galvanized steel or aluminum of the thickness specified in Section 603.4 and the fire-resistance rating is maintained in accordance with the International Building Code. Fire dampers, combination fire/smoke dampers and any similar devices that will obstruct the exhaust flow shall be prohibited in clothes dryer exhaust ducts.

 

[klarenbeek]

At least in the I-codes, if you can't meet any of the exceptions for allowing it without a damper the only other solution is to run it in an independent shaft from the point of penetration to the exterior. The fire wrap used on grease duct is also typically rated as a shaft enclosure so that may be an option.

 

[Plumb-bob]

Thanks for the replies.

The BCBC mentions duct material with a melting point of 760c, is it galvanized ducting that has this melting point?

 

[Inspector Gadget]

You're looking in the wrong section. A dryer cannot vent through another fire compartment, but this determination relies on the interpretation of 'directly' ....

Part 9
9.32.1.3. Venting of Laundry-Drying Equipment
1) Exhaust ducts or vents connected to laundry-drying equipment shall discharge directly to the outdoors.

Or for part 3 buildings
6.3.2.10(9) Exhaust ducts or vents connected to laundry-drying equipment shall discharge directly to the outdoors.

If you're going through a ceiling, there may be an exemption under Appendix D:
D-2.3.10. Ceiling Membrane Openings – Combustible Construction
1) Except as permitted in Article D-2.3.12., where a floor or roof assembly of combustible construction is assigned a fire-resistance rating on the basis of this Subsection and incorporates a ceiling membrane described in Table D-2.3.4.-B, D-2.3.4.-C or D-2.3.4.-D, the ceiling membrane may be penetrated by openings leading to ducts within concealed spaces above the membrane provided:

a) the assembly is not required to have a fire-resistance rating in excess of 1 h,​

b) the area of any openings does not exceed 930 cm 2 (see Sentence (2)),​

c) the aggregate area of openings does not exceed 1% of the ceiling area of the fire compartment,​

d) the depth of the concealed space above the ceiling is not less than 230 mm,​

e) no dimension of any opening exceeds 310 mm,​

f) supports are provided for openings with any dimension exceeding 150 mm where framing members are spaced greater than 400 mm o.c.,​

g) individual openings are spaced not less than 2 m apart,​

h) the ducts above the membrane are sheet steel and are supported by steel strapping firmly attached to the framing members, and​

i) the clearance between the top surface of the membrane and the bottom surface of the ducts is not less than 100 mm.​

Otherwise, D-2.3.10(2) says "fire stop flap" or "fire-rated bulkhead".