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Fire damper for boiler flue

N

nealderidder

Sawhorse
Joined
Dec 7, 2010
Messages
394
Location
Sacramento, CA
I've got a boiler room that is required to be rated (or sprinkled) per table 509 of the CBC. Boiler room is on first floor of a two story building. So I'll have a flue going thru the second floor up to the roof.

Can I put a fire damper on a boiler flue? I'm thinking no (similar to a dryer vent) but can't find the code section telling me I can't.

If I can put a fire damper at the ceiling of the boiler room I could get to the roof without having to construct a rated shaft. I'll still need clearances to combustibles etc. but not an actual rated shaft.

So - can a slap a damper on a flue? If not, can you point me to the code section?

Thanks,
 
Why not just build a rated shaft? Wouldn’t take up much space in the room it passes through.
 
Can you apply exception #3 below? This is how we've done it on one of our local schools that I was involved with.

717.5.2 Fire Barriers
Ducts and air transfer openings of fire barriers shall be protected with approved 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.

Exception: Fire dampers are not required at penetrations of fire barriers where any of the following apply:​
  1. Penetrations are tested in accordance with ASTM E119 or UL 263 as part of the fire-resistance-rated assembly.
  2. Ducts are used as part of an approved smoke control system in accordance with Section 909 and where the use of a fire damper would interfere with the operation of a 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 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. 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.
 
Ty J. said:
Can you apply exception #3 below? This is how we've done it on one of our local schools that I was involved with.

717.5.2 Fire Barriers
Ducts and air transfer openings of fire barriers shall be protected with approved 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.

Exception: Fire dampers are not required at penetrations of fire barriers where any of the following apply:​
  1. Penetrations are tested in accordance with ASTM E119 or UL 263 as part of the fire-resistance-rated assembly.
  2. Ducts are used as part of an approved smoke control system in accordance with Section 909 and where the use of a fire damper would interfere with the operation of a 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 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. 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.
Click to expand...

I would be penetrating a horizontal assembly but there are similar provisions in 717.6.1 (CBC).

So maybe it's not so much that a damper isn't allowed, maybe it's just not often required?
 
nealderidder said:
I would be penetrating a horizontal assembly but there are similar provisions in 717.6.1 (CBC).

So maybe it's not so much that a damper isn't allowed, maybe it's just not often required?
Click to expand...
The section I posted was IBC, so yes, need to verify with the CBC.

I'd suggest that a damper has not been listed for the desired use and that the code provides an exception that can be used to omit a damper in the situation described.
 
Looks like if you damper the vent

You would have to shut down the boiler.

More than likely not an easy task

I don’t think I have seen a damper on a boiler vent
 
As another option, you may be able to use a fire-rated duct wrap similar to a grease duct. This would effectively create a continuation of the fire resistance to the exterior.
 
Any wrap would have to be listed for the use. While there may be a wrap that is listed for use on a flue, I would expect that to be common knowledge if it were true.

A fire damper that is exposed to a boiler flue would need to be sophisticated enough to know the difference between a hot flue and an overheated flue.. An interlock that would interrupt the fuel source feeding the boiler would most likely be a requirement and could negate the need for a damper. All boilers should be so equipped.

Nothing beats a rated shaft.
 
Last edited:
CHECK AGAINST WHAT YOUR BOOK SAYS

607.1.2 Ducts That Penetrate Fire-Resistance-Rated Assemblies Without Dampers

Ducts that penetrate fireresistance-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 International 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 International Building Code.





607.5.5 Shaft Enclosures

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. Steel exhaust subducts extend not less than 22 inches (559 mm) vertically in exhaust shafts provided that there is a continuous airflow upward to the outdoors.
    2. Penetrations are tested in accordance with ASTM E 119 or UL 263 as part of the fire-resistance-rated assembly.
    3. Ducts are used as part of an approved smoke control system in accordance with Section 909 of the International Building Code, and where the fire damper will interfere with the operation of the smoke control system.
 
cda said:
CHECK AGAINST WHAT YOUR BOOK SAYS

607.1.2 Ducts That Penetrate Fire-Resistance-Rated Assemblies Without Dampers

Ducts that penetrate fireresistance-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 International 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 International Building Code.





607.5.5 Shaft Enclosures

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. Steel exhaust subducts extend not less than 22 inches (559 mm) vertically in exhaust shafts provided that there is a continuous airflow upward to the outdoors.
    2. Penetrations are tested in accordance with ASTM E 119 or UL 263 as part of the fire-resistance-rated assembly.
    3. Ducts are used as part of an approved smoke control system in accordance with Section 909 of the International Building Code, and where the fire damper will interfere with the operation of the smoke control system.
Click to expand...
Who is this directed at and what is your point? Who/what does not align with the code?
 
No you cannot put a fire damper in a boiler flue, for several reasons:
1. I no of no fire dampers rated for the temperatures present in a boiler vent.
2. IFGC 503.15 prohibits any device that can retard the flow of flue gases with a few specific exceptions, none of which are fire dampers.
3. All factory built metal chimney/vent systems are UL listed systems with NO provisions for fire dampers because of #1 above and its just a REALLY BAD idea.

As far as using the fire wrap in lieu of a shaft, there are also several problems. As far as I know, the wrap is listed for use on duct only, not on gas appliance vents. Also, all vent systems out there that I know of and the IFGC require airspace clearance to combustibles AND insulation. Vent system manufacturers usually specifically prohibit applying any type of insulation to the vent system. Vent pipes can't be insulated because thye require the airspace around them to help disperse heat.

A drywall shaft will be required, no other option is available. The boiler room will have to be built with the same rating as the shaft since the shaft opens into the room with no protection.
If the boiler is vented using PVC, you can use listed through penetration firestops designed for the size of the pipe used.
 
A quick search on WWW I found several products that may be listed for wrapping the flue pipe, also there are listed products for flue with minimal clearance requirements.
stop trying to reinvent the solution ask a manufacturer of wrap products or flue pipes to offer a solution.
 
If the vent is vertical floor to ceiling (of a room?), in what way is it protected from impact?
 
First step would be to determine what the boiler "flue" actually consists of. You need to consult the boiler installation instructions to determine this.

As I said, most listed gas vent pipe/chimney systems prohibit wrapping them in any kind of insulation. It doesn't matter what the insulation material says, you can't violate the listing of the vent system. Besides, UL listed systems are almost always listed for clearances ranging from 1-3 inches anyway so you gain almost nothing trying to wrap them to reduce clearances.

As far as protecting the vent from impact, in this situation it is going to have to be in a rated drywall shaft from the point it exits the boiler room until it exits the building. Even in situations where the rated shaft isn't required, most metal vent system manufacturers (and common sense) require the vent to be in an enclosure of some sort where it goes through finished areas of a building both to protect the vent and maintain required clearance to combustibles. That way you can't stack cardboard boxes or towels right up against it.
 
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