Smoke Detection Above Ceiling

[jc23]

I install fire alarm systems in New Jersey. Although I know this isn't a NEC question, I have not found many forums to post fire related questions, and it seems like there might be a few people here that might be able to help me.

Are there any instances where total converage is not required even when an automatic fire alarm system is for the use group of the building? And is there any exception to the requirement of installation of smoke detectors above a drop ceiling?

I ask because although I always install smoke detection above ceilings as per NFPA 72's definition of total coverage (NFPA 72 2007, 5.5.2.1), for small installations where there is no spec to follow, I am often underbid by companies that do not install smoke detection above the ceiling and they are rarely required to do so by the AHJ.

I would appreciate any help on this matter, because it seems to be one of those issues that is not clearly defined by the codes and is often overlooked by the AHJ.

Thanks,
John

 

[peter d]

In my area we are required to install heat detectors, not smoke detectors, above suspended ceilings above a certain height (I'm not sure of the exact number because the jobs I work on are usually exempt.)

I wouldn't want a smoke detector above a suspended ceiling anyway because it would get fouled with dirt pretty quickly, and assuming you're using a conventional (non addressable) system it would be difficult to locate the initiating device in an alarm event.

 

[MichaelGP3]

In my area we are required to install heat detectors, not smoke detectors, above suspended ceilings above a certain height .....

I wouldn't want a smoke detector above a suspended ceiling anyway because it would get fouled with dirt pretty quickly, and assuming you're using a conventional (non addressable) system it would be difficult to locate the initiating device in an alarm event.

I haven't performed installations that have this requirement myself, but I imagine it would be treated the same as underfloor smoke detectors installed in data rooms/server farms, where the individual detectors are displayed on a graphic annunciator. If this isn't in the contract, a red alarm LED on a single gang plate on the wall or on a ceiling tile below the smoke detector should be figured into the bid.

I'm not sure how large this space would have to be to make a VESDA system attractive, when the costs of future servicing and inspections are taken into account.

 

[Lcdrwalker]

Here in Ohio we don't install detectors above a suspended ceiling. If this area is used as a plenum, a detector in the return side of HVAC unit is considered adequate.