fire/smoke damper for bathroom exhaust

[nietzj]

I have a project to wire a simple bathroom exhaust fan in a commercial building that is being vented directly outside the building. The sheet metal contractor is telling me it needs a fire/smoke damper but I'm pretty sure if it is being directly exhausted outside the building whats the point of keeping the smoke inside. Any help would be appreciated.

 

[mgookin]

If it passes through a rated assembly then you need a rated damper.

 

[gadfly56]

If it passes through a rated assembly then you need a rated damper.

That makes absolutely no sense. Are all the windows and exterior doors in a commercial building fire rated? :happyno:

 

[luckylerado]

I have a project to wire a simple bathroom exhaust fan in a commercial building that is being vented directly outside the building. The sheet metal contractor is telling me it needs a fire/smoke damper but I'm pretty sure if it is being directly exhausted outside the building whats the point of keeping the smoke inside. Any help would be appreciated.

Not sure if it applies but here is some info from IBC to consider:

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.
140
Exceptions: In occupancies other than Group H, fire
dampers are not required where any of the following
apply:
1,2,3,

4. Such walls are penetrated by ducted HV AC 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
HV AC system shall be a duct system for conveying
supply, return or exhaust air as part of the
structure's HV AC 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.

 

[mgookin]

That makes absolutely no sense. Are all the windows and exterior doors in a commercial building fire rated? :happyno:

What part didn't you understand?
The part about passing through a rated assembly?
Or having to be rated if it does pass through a rated assembly?

The integrity of a fire rated assembly must be maintained.
Penetrate it and you have to protect that penetration.

To answer your question, if that wall is rated, then the opening needs to be rated. We call that an opening protective.
But why would you say "...all the windows and exterior doors..." Most exterior walls are not rated; some are.

 

[dkidd]

That makes absolutely no sense. Are all the windows and exterior doors in a commercial building fire rated? :happyno:

Yes, generally.

705.5 Fire-resistance ratings.
Exterior walls shall be fire-resistance rated in accordance with Tables 601 and 602 and this section. The required fire-resistance rating of exterior walls with a fire separation distance of greater than 10 feet (3048 mm) shall be rated for exposure to fire from the inside. The required fire-resistance rating of exterior walls with a fire separation distance of less than or equal to 10 feet (3048 mm) shall be rated for exposure to fire from both sides.

 

[gadfly56]

Yes, generally.

705.5 Fire-resistance ratings.
Exterior walls shall be fire-resistance rated in accordance with Tables 601 and 602 and this section. The required fire-resistance rating of exterior walls with a fire separation distance of greater than 10 feet (3048 mm) shall be rated for exposure to fire from the inside. The required fire-resistance rating of exterior walls with a fire separation distance of less than or equal to 10 feet (3048 mm) shall be rated for exposure to fire from both sides.

Please note that a DOOR or a WINDOW is not a WALL.

 

[gadfly56]

What part didn't you understand?
The part about passing through a rated assembly?
Or having to be rated if it does pass through a rated assembly?

The integrity of a fire rated assembly must be maintained.
Penetrate it and you have to protect that penetration.

To answer your question, if that wall is rated, then the opening needs to be rated. We call that an opening protective.
But why would you say "...all the windows and exterior doors..." Most exterior walls are not rated; some are.

Which part of "vented directly outside" did you not understand? I read the OP's question as the bathroom exhaust penetrates the EXTERIOR wall only, and you think it needs a fire/smoke damper at that boundary???

Now, if on its way it passes through an INTERIOR fire partition, then yes, it could need a fire/smoke damper.

 

[dkidd]

Please note that a DOOR or a WINDOW is not a WALL.

They are components of the walls.

 

[raider1]

Is the bath fan penetrating a rated floor ceiling assembly prior to going through the exterior wall?

Chris

 

[gadfly56]

They are components of the walls.

No, they are not. Note that in a 2-hour fire rated wall, you can have a 1-1/2 hour rated door.

Before you get too far off course, we are talking here about a fart fan that's (probably) mounted in the exterior wall or ducted to the exterior wall without leaving the bathroom. Still think it needs a fire/smoke damper?

 

[dkidd]

Are all the windows and exterior doors in a commercial building fire rated??

Note that in a 2-hour fire rated wall, you can have a 1-1/2 hour rated door.

Huh?

 

[gadfly56]

Huh?

With regard to the fire door, please see Table 716.5 in the 2012 edition of the IBC.

Did you read the second paragraph of my post #11 before we get into the weeds regarding the required ratings of penetrations in fire walls?

 

[ike5547]

Please note that a DOOR or a WINDOW is not a WALL.

I'm not a carpenter, but I've been under the impression that doors (never even thought about windows) are required to be rated the same as the walls.

 

[gadfly56]

I'm not a carpenter, but I've been under the impression that doors (never even thought about windows) are required to be rated the same as the walls.

Please see table 716.5 in the 2012 edition of the IBC. See table 705.8 for the requirements for exterior walls.

 

[raider1]

Again if the fart fan is cut into a rated floor/ceiling assembly then the opening would have to have a listed ceiling radiation damper. See IBC 717.6.2 for membrane penetrations of a horizontal assembly.

As for a smoke damper, that is not required unless we are penetrating a smoke barrier or smoke partition.

Chris

 

[mgookin]

Please note that a DOOR or a WINDOW is not a WALL.

It's an opening. In most cases the rating of the opening can be less than that of the rating of the wall. Sometimes it has to be the same. I doubt OP is running duct through a door or window so this is moot.

I don't understand why OP is having to deal with this. It is mechanical construction. All OP should have to do is run the branch circuit.

 

[gadfly56]

It's an opening. In most cases the rating of the opening can be less than that of the rating of the wall. Sometimes it has to be the same. I doubt OP is running duct through a door or window so this is moot.

I don't understand why OP is having to deal with this. It is mechanical construction. All OP should have to do is run the branch circuit.

If it's a smoke damper it's going to have a motor on it. It's always a tussle who supplies this item; the fire alarm company, the mechanical contractor, or the electrical contractor. No one wants to own it.

 

[Smash]

I believe the objective is to keep any and all outside air out from a burning building. Fresh air of any kind feeds the flames. If every single thing was sealed up, dampers etc. might not burn at all once the initial oxygen is gone. That's why suppression systems are put in commercial kitchens limit the oxygen exposure the fire can be contained to the kitchen not spread to the patrons sitting 50ft away. As far as a little fart fan I agree take it easy but the line needs to be drawn somewhere and in your case it was. Did you tell the inspector that it's just a fart in the wind ?? sorry it needed to be said.

 

[gadfly56]

I believe the objective is to keep any and all outside air out from a burning building. Fresh air of any kind feeds the flames. If every single thing was sealed up, dampers etc. might not burn at all once the initial oxygen is gone. That's why suppression systems are put in commercial kitchens limit the oxygen exposure the fire can be contained to the kitchen not spread to the patrons sitting 50ft away. As far as a little fart fan I agree take it easy but the line needs to be drawn somewhere and in your case it was. Did you tell the inspector that it's just a fart in the wind ?? sorry it needed to be said.

I don't think you understand how kitchen suppression systems work. They do not "limit the oxygen exposure", they put the fire out (if properly designed and maintained). The chemical agent reacts with the grease to form a foam that smothers the fire and the water in the agent cools metal surfaces to prevent re-flash. Typically, the exhaust system remains on, but make up air, if provided by a make up air unit, is shut down. No dampers are typically involved, so air can continue to flow through the MUA as if it were a simple hole in the roof. It just doesn't get a boost on the way in.

Please see the tables I referred to in the IBC. For a commercial structure at 5-10 foot separation, you can have up to 10% of the wall area as unprotected openings.