Smoke detector placement near a bulkhead - see sketch

[bbaumer]

Hi all.

Is there a minimum distance a smoke detector needs to be away from a bulkhead? I have an application where we are adding some piping and covering it with SoffiSteel steel soffit creating a bulkhead of sorts down the center of the room in the dimension shown near an existing smoke detector. I could not find anything in NFPA 72 addressing this.

Looking for minimum distance of "d" in the sketch, if there is one.

Thanks.

 

[electricmanscott]

Not sure about code but manufacturers usually have a location requirement that addresses this.

 

[bbaumer]

These are System Sensor heads on a Notifier system.

I looked at this install guide from System Sensor but it just re-hashes NFPA72:

http://www.systemsensor.com/pdf/A05-1003.pdf

I think I have created a "beam" less than 12" in depth and can ignore it so dimension "d" can be anything but want to be sure.

 

[mcclary's electrical]

These are System Sensor heads on a Notifier system.

I looked at this install guide from System Sensor but it just re-hashes NFPA72:

http://www.systemsensor.com/pdf/A05-1003.pdf

I think I have created a "beam" less than 12" in depth and can ignore it so dimension "d" can be anything but want to be sure.

The fire marshall wants it to be further than 12" off the wall.

When you mount on the wall vertically, they make you stay a minimum of 6" away from the ceiling. The same "dead air" spot occurs on the ceiling that occurs down the wall, due to the corner.

 

[1793]

These are System Sensor heads on a Notifier system.

I looked at this install guide from System Sensor but it just re-hashes NFPA72:

http://www.systemsensor.com/pdf/A05-1003.pdf

I think I have created a "beam" less than 12" in depth and can ignore it so dimension "d" can be anything but want to be sure.

I would look at the fig. on pg 10. If I was doing this I would move the Sensor out at least 4" from the beam, if that is what I see in your sketch.

 

[LarryFine]

I've always used at least 12" down or away from a wall-ceiling junction.

 

[Chamuit]

I would probably do 9". The length of the hypotenuse of a 6.5 by 6.5 triangle.

[random thought] I thought unless there was a 24" difference in elevation . . . that comes into play?

 

[LarryFine]

I would probably do 9". The length of the hypotenuse of a 6.5 by 6.5 triangle.

Is that a fancy way of saying "at least the beam height"? :grin:

 

[gadfly56]

These are System Sensor heads on a Notifier system.

I looked at this install guide from System Sensor but it just re-hashes NFPA72:

http://www.systemsensor.com/pdf/A05-1003.pdf

I think I have created a "beam" less than 12" in depth and can ignore it so dimension "d" can be anything but want to be sure.

The only information available on smoke detector spacing is in section 5.7.3.2.4 of the 2002 edition of NFPA 72. From your illustration, I presume this is a singular beam, not a repeated pattern. You are correct that NFPA 72 doesn't directly address your situation. You could make the worst case assumption and treat the beam as a wall. In that case, distance "d" would need to be 4". Unless of course the beam height is more than %10 of the floor to ceiling distance and the distance from the beam to a parallel wall is more than %40 of the floor-to-ceiling height, then you need to put a smoke detector in each bay. Somehow, I don't see this room being less than 5' 5" in height :grin:!

 

[bbaumer]

The only information available on smoke detector spacing is in section 5.7.3.2.4 of the 2002 edition of NFPA 72. From your illustration, I presume this is a singular beam, not a repeated pattern. You are correct that NFPA 72 doesn't directly address your situation. You could make the worst case assumption and treat the beam as a wall. In that case, distance "d" would need to be 4". Unless of course the beam height is more than %10 of the floor to ceiling distance and the distance from the beam to a parallel wall is more than %40 of the floor-to-ceiling height, then you need to put a smoke detector in each bay. Somehow, I don't see this room being less than 5' 5" in height :grin:!

This is how I see it as well. Not addressed so d could be anything.

Floor to ceiling is roughly 8'0", maybe a few inches more so that does not apply.

Thanks to all for the replies.

 

[charlietuna]

I would consider a minimum of 24 inches for figure "D". The area of 6 inches down from the ceiling and 24 inches from the beam is considered a dead air space--from what i've been told !

 

[gadfly56]

I would consider a minimum of 24 inches for figure "D". The area of 6 inches down from the ceiling and 24 inches from the beam is considered a dead air space--from what i've been told !

This is the putative reason for the 4" x 4" rule we currently have. I have heard rumors to the effect that someone has conducted testing which shows that the floor/ceiling interface does not, in fact, produce a "dead zone" and that the rules on smoke detector placement in the 2010 edition of NFPA 72 reflect this new information. Can anyone confirm or debunk this rumor? I don't have a copy of the 2010 edition yet.

 

[nhfire77]

YES!!


Holy Crap. I hadn't read it completely, but I looked that up. There is a new drawing showing there is no more gap in the corner

17.7.3.2.1 Spot type smoke detectors shall be located on the ceiling or, if on a side wall, between the ceiling and 12 in. (300mm) down from the ceiling to the top of the detector.

 

[bbaumer]

YES!!


Holy Crap. I hadn't read it completely, but I looked that up. There is a new drawing showing there is no more gap in the corner

17.7.3.2.1 Spot type smoke detectors shall be located on the ceiling or, if on a side wall, between the ceiling and 12 in. (300mm) down from the ceiling to the top of the detector.

I looked it up too. The 4" rule is gone. You can put the smoke anywhere on the ceiling even right up next to the wall.

Alas, Indiana is still under the 2002 version, let alone the 2010.....

 

[DM2-Inc]

This is the putative reason for the 4" x 4" rule we currently have. I have heard rumors to the effect that someone has conducted testing which shows that the floor/ceiling interface does not, in fact, produce a "dead zone" and that the rules on smoke detector placement in the 2010 edition of NFPA 72 reflect this new information. Can anyone confirm or debunk this rumor? I don't have a copy of the 2010 edition yet.

The rule for Smoke Detectors was changed, as others have noted, however the rule for heat detector placement in the corners remains the same. The change was precipitated as the result of testing performed by the "Fire Protection Research Foundation", and published in 2007. The report is available on both NFPA's Web site, and UL's Web Site.