American Fire Sprinkler Association
12750 Merit Drive, Suite 350 * Dallas TX 75251
Ph: (214) 349-5965 Fax: (214) 276-0908
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TECHNICAL UPDATE
June 6, 2007
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"A light hazard building had a ceiling height of 12 ft - 4 in. above
finished floor was supplied with sprinklers designed at 0.1/1,500 sf
with heads spaced at 125 sf max. flowing 12 heads. A tenant moved in
adding multiple light hazard offices with ceilings approximately 10
ft above finished floor. Can we use the small room application
knowing we will have heads spaced at least 7 ft - 6 in. off three
walls and 9 ft off one wall?
We have reviewed NFPA 13, 2002 edition, as the applicable standard.
Our informal interpretation is that your proposed arrangement is not
acceptable since the maximum area of coverage per sprinkler is
exceeded and it appears you are exceeding 7'6" from more than one wall.
The small room design as dictated by 13:8.6.3.2.4 explicitly allows
us to exceed the maximum spacing allowance of 7'6" to one wall but
the area of coverage and the allowed spacing to the other walls and
sprinklers shall not be exceeded. So you can space up to 7'6" to the
other walls, whereas you said spaced "at least" 7'6". In calculating
the area of coverage, you simply take the area of the room and divide
it by the number of sprinklers. The SxL rules do not apply but the
maximum spacing dimensions must still be applied
If the area of the room calculates to 247 sf, that exceeds the 225 sf
maximum area of coverage for a single sprinkler. Two sprinklers
would be needed for the room unless a quick response extended
coverage sprinkler is used (for which the small room rule does not
apply). As an example, Figure A.8.6.3.2.4 (b) shows two sprinklers
each 9 ft - 0 in. off one wall and 6 ft - 0 in. off the opposite, 15
ft between sprinklers, and 7 ft - 6 in. off each adjacent wall. This
results in an area of coverage per sprinkler of 225 sf which is the
maximum. The 6 ft dimension is imposed solely based on the maximum
area of coverage for two sprinklers. Once you have selected a wall
that you exceed the 7'6" restriction, you are set in that direction
and cannot exceed the 7 ft - 6 in. maximum in any other direction.
In other words, if you space the sprinkler 8 ft - 0 in. off one wall,
you cannot then also be 8 ft - 0 in. off the opposite wall even
though 16 ft - 0 in. is less than the 16 ft - 6 in. resulting when
you're 9 ft - 0 in. off one wall and 7 ft - 6 in. off the other.
Another limitation that should be noted is that the total room area
cannot exceed 800 sf.
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Technical Update is prepared by the Technical Services Dept. of the
AFSA: Vice President of Engineering and Technical Services Roland
Huggins, a PE registered in fire protection engineering; Phill Brown,
a NICET IV certified automatic sprinkler technician and NFPA
Certified Fire Protection Specialist (CFPS) and Tom Wellen, a degreed
fire protection engineering technologist. This is provided with the
understanding that the AFSA assumes no liability for this opinion or
actions taken on it and they are not to be considered the official
position of the NFPA or its technical committees.
Copyright (c) 2007, American Fire Sprinkler Association. All
Rights Reserved
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