NFPA72 smoke detector spacing reduction dut to heigth
NFPA72 smoke detector spacing reduction dut to heigth
(OP)
Hello to every body.
Reading NFPA72 2002 edition, I cannot find to reference for the spacing reduction for spot tipe smoke detectors due to ceiling height.
I´ve been told to use the same heigth reduction that is indicated for heat detectors on table 5.6.5.5.1 ("Heat detector spacing reduction based on ceiling heigth"), but I cannot find the mention in the code that clarify how to apply a reduction for smoke detectors.
Any help, thanks a lot in advance.
Reading NFPA72 2002 edition, I cannot find to reference for the spacing reduction for spot tipe smoke detectors due to ceiling height.
I´ve been told to use the same heigth reduction that is indicated for heat detectors on table 5.6.5.5.1 ("Heat detector spacing reduction based on ceiling heigth"), but I cannot find the mention in the code that clarify how to apply a reduction for smoke detectors.
Any help, thanks a lot in advance.





RE: NFPA72 smoke detector spacing reduction dut to heigth
if there it has to be in the smoke detector section on spacing
RE: NFPA72 smoke detector spacing reduction dut to heigth
and fiqure a.5.6.5.1.2 not sure about ceiling height though
as always you have to install per manufacture so you might start there first.
RE: NFPA72 smoke detector spacing reduction dut to heigth
Thanks,
RE: NFPA72 smoke detector spacing reduction dut to heigth
If you are talking about smoke alarms in a house the answer would be yes,
RE: NFPA72 smoke detector spacing reduction dut to heigth
Sorry, hotel corridor.
RE: NFPA72 smoke detector spacing reduction dut to heigth
RE: NFPA72 smoke detector spacing reduction dut to heigth
RE: NFPA72 smoke detector spacing reduction dut to heigth
did you look at the sections I sited??
RE: NFPA72 smoke detector spacing reduction dut to heigth
ok here you go
look at 5.7.3.2.3 (E) and A.5.7.3.2.3(E) 2002 edition
which once again refers you to fiquire A.5.6.5.1(a) to A.5.6.5.1(g) and A.5.6.5.1.2
Do the math
RE: NFPA72 smoke detector spacing reduction dut to heigth
Going back; the doubt is this: it is clear for heat detectors that the ceiling heigth reduction is applied thru table 5.6.5.5.1. but for smoke detectors do I have to apply a reduction due to height???
Recently and reading the code better I found that in A.5.7.3.2.4(B):
"A.5.7.3.2.4(B) The spacing guidelines in 5.7.3.2.4(B) are based on a detection design fire of 100 kW. For detection at a larger 1-MW fire and ceiling heights of 8.53 m (28 ft) or less, smooth ceiling spacings should be used and the detectors can be located on the ceiling or the bottom of the beams."
So it looks that the answer is hidden in this apendix parragraph: looks like there is no need to apply a ceiling heigth reduction due to the fact that the spacing for smoke detectors is the same for ceilings up to 28ft. For me it is not totally clear but is the only thing I have found.
My doubt comes from a NFPA 72 seminar, the instructor mentioned to reduce spacing due to height the same way for heat or smoke detector with table 5.6.5.5.1., but now I have the doubt since I have come across with a particular case.
Other way you can help me in this matter is about your experience: ¿what do you do with spot type smoke detector spacing when you have ceiling heights in the order of 5(17ft) to 8m (26 ft)? Do you use the same "S" as it was a 3m (10ft) ceiling?
Am I missing something obvius??? Please tell, for me it´s better to make a ridicule for being corrected in order to learn.
RE: NFPA72 smoke detector spacing reduction dut to heigth
look at fiqure A.5.6.5.1g This is what I am use to spacing from 30 feet to 41 feet depending on shape.
The only other thing is to contact maker of smoke detector to see if thier listing allows adjustments due to ceiling.
RE: NFPA72 smoke detector spacing reduction dut to heigth
RE: NFPA72 smoke detector spacing reduction dut to heigth
RE: NFPA72 smoke detector spacing reduction dut to heigth
RE: NFPA72 smoke detector spacing reduction dut to heigth
However, what matters is the "stratification" of smoke in high ceiling spaces. I believe there is some discussion on this in NFPA. Heat keeps rising until a ceiling obstructs it or the air cools down to its surroundings temperature. But smoke can just "hang" in somewhere in the middle and not reach the ceiling, like smog (stratification), if the air not moving. One of the solutions is to have multiple levels (staggered height) of smoke detectors in such spaces.
RE: NFPA72 smoke detector spacing reduction dut to heigth
to me it is a specification issue or ahj issue
nfpa tells you how to install it
the specs or ahj tell you what is required