# Area Smoke detector with Return air duct detection



## Brookhaven 58 (Jan 26, 2012)

I am looking for a little clarification if possible with regards to Section 606.2 of MC of NYS 2010 ed, which should be ICC 2006 ed:

EXception states "Smoke detectors shall not be required where air distribution systems are incapable of spreading smoke beyond the enclosing walls, floors and ceilings of the room or space in which the smoke is generated. "

1.  Are the smoke detectors being referred to Area or Duct ?

2.  With respect to  "Incapable of spreading" is that equivalent to HVAC being equipped with fan shutdown and upon alarm activation, smoke is no longer circulated.

I my be answering my own question here; with common return duct from multiple rooms and no circulation within the HVAC, smoke could spread from room to room through the common duct work unless equipped with electric dampers.

Any help would be appreciated.


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## codeworks (Jan 26, 2012)

hi, to # 1, yes duct detection, which answers # 2, yes,  the duct detector shuts down the fan, thereby eliminating the chance of further spred of smoke.


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## cda (Jan 26, 2012)

I say it is saying if the smoke will not spread from one portion of a building to another

Like a big box store or warehouse, where you basically have one big room, so there is no other place to go, except that one room//area


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## Builder Bob (Jan 26, 2012)

I believe the intent would be something along the lines of having a HVAC system in a big box store....... Since the smoke isn't going to be pushed, shoved, or restricted from migrating due to the openness of the sales floor area, it isn't required by code as the exception allows.

However, if a HVAC system serves both areas - office area and sale floor area, then HVAC shutdown is required.

HVAC shutdown can be performed by either method - duct or area detectors.

The only thing that needs clarification from the AHJ is what they consider area detection. (IMHO, a fully compliant NFPA 72 automatic fire alarm system in all areas in the entire structure......)

( my interpretation may be different that my brother Barry's in another state --- I am fire service background and understand fire development and smoke movement fairly well, My other brother Barry was a Builder with a Contractor/politician Background..... Our answers may vary greatly.)


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## gbhammer (Jan 26, 2012)

I agree with cda.

However all of the big box stores I have ever reviewed have smoke detectors and shutdowns at all of their RTU returns.


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## klarenbeek (Jan 26, 2012)

I agree no detection is needed in the big box store scenario if there are no runs feeding other areas.

As far as area detection for shutdown, if you keep reading (at least in the IMC) the next section requires duct smoke detection with this exception:

Smke detectors are not required in the return air systemwhere all portions of the building served by the air distribution system are protected by area SMOKE (not fire) detectors connected to a fire alarm system.

The fire alarm system would then have to shut down the air handlers


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## rnapier (Jan 27, 2012)

I have seen this exception used often from warehouses where dust was an issue to controled environments where positive pressure is maintained for clean rooms.


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## Msradell (Jan 27, 2012)

The problem with not having detection even in a big boxed store situation is that the small will be spread throughout the entire store and trip multiple smoke detectors.  If the HVAC systems are shut down immediately it will be easier to determine where the smoke is coming from (if just smoke not a large fire) because the smoke detectors that are in alarm status will initially be concentrated in one area.


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## cda (Jan 27, 2012)

Mar

But it is not normally required

The idea in a wide open place someone will hopefully see the fire


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## TheCommish (Jan 27, 2012)

smoke dectction in duct not requierd if system exaust to outside, or bringing air in from outside, and the units is less than 2000 cfm. I would say in a big box RTU that recurlates air in the building duct smoke and shutdown is required see NFPA on construction of HVAC systems that is where I find the requiement for duct smokes  by refrence in Mass.


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## klarenbeek (Jan 30, 2012)

depends what codes are adopted in your jurisdiction. Even though it may be a good idea, IMC does not require shutdown in a big box store.  As an inspector, I can't require it under the IMC.


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