Fire rated ceiling and dampers?

[John_187]

There is an elevator machine room on this project. It has fire rated walls and fire rated ceiling. There are 2 exhaust grilles in the fire rated ceiling. These exhaust grilles then combine into a single duct that passes through the fire rated wall. The duct passing through the fire rated wall has a fire damper. But do the two exhaust grilles require a fire damper as well?

I was starting to look for a code that might say, haven't found anything so far.

Please provide any input if you know about this situation, thanks

 

[dbill74]

Are they "exhaust" or "return"? Pretty sure "exhaust" is not allowed to have dampers at all.

If they are "return" air, then the grilles wouldn't need dampers if there is a fire damper in the rated wall.

I'd also be asking the architect why the ceiling is rated? What floor is the machine room on? (Why is there even a ceiling?)

 

[GT-EGR]

Not sure what state you are in, but in the mechanical code, exhaust chapter, you can find which systems are not allowed to have fire dampers installed - clothes dryers, hazardous exhaust, kitchen exhaust, maybe a few others. Any general exhaust can have a fire damper just like a supply or return gets one.

If it doesn't create a more dangerous situation by having a damper close in a fire event, you should put in the damper. So if this is exhaust a machine room just to cool it, and there isn't anything hazardous within the room, you likely should have a damper.

As far as the rated ceiling vs wall, it's unclear why a ceiling would be rated, if the walls surrounding the room are rated as well. But if both are rated, both probably need a damper. Unless the duct meets some of the exceptions to not require a damper, which depending on the wall type is possible if ducts are all steel of a certain thickness, and under a certain duct size, fully sprinklered, etc.

 

[trashcanman]

Better put the fire dampers in. This will avoid a change order later.