American Fire Sprinkler Association
12750 Merit Dr., Suite 350 Dallas TX 75251
Ph: (214) 349-5965 Fax: (214) 276-0908
TECHNICAL UPDATE
APRIL 4, 2007
A diagram was attached that shows a storage area under a manager's
apartment. There are six storage units measuring 10 ft. by 10 ft.
and two storage units measuring 5 ft, by 10 ft. The area of the
openings is 49.3 sq. ft. and provided with 2 ft. 6-in. lintels. Nodes
D201 through D204 are shown in a corridor to the storage rooms. Nodes
2A through 9A are shown in the storage areas. A 4-hour rated C.M.U.
firewall is provided as a horizontal separation from the other
residential units. You asked the following question,
"The first floor under the manager's apartment is a storage area. We
have calculated the corridor nodes D201 through D204 as the most
hydraulically demanding area. The AHJ is requiring all heads in the
storage area (D201 through D204, 2A through 9A) to be calculated per
6.7.2.1. Is this correct?"
We have reviewed the 2002 edition of NFPA 13R that you indicated as
the applicable standard. Our informal interpretation is that a
design based upon all the sprinklers within the compartment but not
exceeding four sprinklers can be applied.
There are several equally acceptable methods and the method selected
is at the discretion of the designer unless there is a local
amendment modifying NFPA 13R. Section 6.7.2.1 states, "For areas
outside the dwelling unit, the following criteria shall comply with
specifications in NFPA 13, unless permitted by 6.7.2.2 and 6.7.2.3:
(1) Design Discharge, (2) Number of design sprinklers, (3) Sprinkler
coverage, (4) Position of sprinklers." So if you meet the criteria
specified in section 6.7.2.2, it can be applied. Section 6.7.2.2
states, "The system demand of areas outside the dwelling unit shall
be permitted to be limited to the number of sprinklers in the
compartmented area but shall not be greater than the demand for a
total of four sprinklers where all of the following conditions are met:
(1) The area is compartmented into areas of 500 ft2 or less by 30-
minute fire-rated construction.
(2) The area is protected by quick-response or residential sprinklers
not exceeding 130 ft2 per sprinkler for ordinary hazard, 225 ft2 for
light hazard, or the allowable coverage of the sprinkler listing.
(3) Openings have a lintel at least 8 inch in depth.
(4) The total area of openings does not exceed 50 ft2 for each
compartment.
(5) Discharge densities are in accordance with NFPA 13, Standard for
the Installation of Sprinkler Systems."
According to the commentary text in the NFPA 13 Handbook, paragraph
6.7.2.2 provides an alternative to the design area criteria of NFPA
13. This alternative is an adaptation of the room design method of
11.2.3.3 of NFPA 13. The 130 sq. ft. area of coverage in 6.7.2.2(2)
is based in part on the assumption that the areas that will be
protected in accordance with 6.7.2.2.
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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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