# NFPA 72 - Beam Pockets above Suspended ceiling



## NJWVUGrad (May 12, 2011)

Working in Nassau county, NY where we are designing for Above Ceiling smoke detectors where the ceiling above has beam pockets.

My question is when the NFPA references ceiling height, is it the height above the drop ceiling or the height above finished floor. It mentions that when installing devices above a suspended ceiling it should be treated as a seperate room. But it doesn't mention anything about where to take the ceiling height reference from in that scenario.


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## joebanana (Dec 21, 2010)

The drop ceiling is ceiling height. The clue is "above suspended ceiling". What's a spoke detector?


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## Cow (Jan 16, 2008)

joebanana said:


> What's a spoke detector?


It's a deal they use when manufacturing bicycle, motorcycle and similar wheels.

Not sure what bike wheels have to do with drop ceilings though....?


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## NJWVUGrad (May 12, 2011)

Very funny.

It's most certainly not the drop ceiling height.

What I am trying to determine is, if it is the ceiling/deck height above the suspended ceiling or above the finished floor.


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## joebanana (Dec 21, 2010)

NJWVUGrad said:


> Very funny.
> 
> It's most certainly not the drop ceiling height.
> 
> What I am trying to determine is, if it is the ceiling/deck height above the suspended ceiling or above the finished floor.


Typically, ceiling height is measured from floor to underside of the roof. Clear ceiling height is from floor to lowest hanging object from the ceiling. ie. drop ceiling. 9 feet is standard. Room height is from floor to hard lid. What does it say about plenum ceilings?


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## joebanana (Dec 21, 2010)

Cow said:


> It's a deal they use when manufacturing bicycle, motorcycle and similar wheels.
> 
> Not sure what bike wheels have to do with drop ceilings though....?


Apparently, he _mis-_spoke, now it's a "smoke detector". Not sure what that has to do with bike tires, either??


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## MechanicalDVR (Dec 29, 2007)

NJWVUGrad said:


> Working in Nassau county, NY where we are designing for Above Ceiling smoke detectors where the ceiling above has beam pockets.
> 
> My question is when the NFPA references ceiling height, is it the height above the drop ceiling or the height above finished floor. It mentions that when installing devices above a suspended ceiling it should be treated as a seperate room. But it doesn't mention anything about where to take the ceiling height reference from in that scenario.


Ceiling height is deck to ceiling (ie drop ceiling).

YES the space above the drop ceiling is a separate area, not having common air flow with the space below the ceiling unless it's used as a return plenum.

***Were you in a panic? I see this is posted like in several forums?


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## Wardenclyffe (Jan 11, 2019)

Speak,

unless 

Spoke n too,...


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