NFPA 13 (2010) section 11.1.2* and the newly added appendix section gives an
example of how to determine the remote area size for adjacent hazards, what it
does not include is quick response reduction in the portion of the hazard area
that is OH2 or less. Is it appropriate to use Quick Response area reduction as
allowed by other sections of the standard in a portion of a design area when
the ceiling is less than 20 ft AFF over the entire floor in question? As a
follow up, is it known why QR cannot be used in Extra Hazard occupancies per
sections 8.4.1.2, 11.2.3.2.2.2, 11.2.3.2.3.1(2), and 12.6.6?
11.1.2* Adjacent Hazards or Design Methods. For buildings
with two or more adjacent hazards or design methods, the
following shall apply:
(1) Where areas are not physically separated by a barrier or
partition capable of delaying heat from a fire in one area
from fusing sprinklers in the adjacent area, the required
sprinkler protection for the more demanding design basis
shall extend 15 ft (4.6 m) beyond its perimeter.
(2) The requirements of 11.1.2(1) shall not apply where the
areas are separated by a barrier partition that is capable of
preventing heat from a fire in one area from fusing sprinklers
in the adjacent area.
A.11.1.2 The situation frequently arises where a small area of a
higher hazard is surrounded by a lesser hazard. For example,
consider a 600 ft2 (55.7m2) area consisting of 10 ft (3.05 m) high
on-floor storage of cartoned unexpanded plastic commodities
surrounded by a plastic extruding operation in a 15 ft (4.57 m)
high building. In accordance with Chapter 12, the density required
for the plastic storage must meet the requirements for
extra hazard (Group 1) occupancies. The plastic extruding operation
should be considered an ordinary hazard (Group 2) occupancy.
In accordance with Chapter 11, the corresponding discharge
densities should be 0.3 gpm/ft2 (12.2 mm/min) over
2500 ft2 (232m2) for the storage and 0.2 gpm/ft2 (8.1 mm/min)
over 1500 ft2 (139 m2) for the remainder of the area. (Also see
Chapter 11 for the required minimum areas of operation.)
If the storage area is not separated from the surrounding
area by a wall or partition (see 11.1.2), the size of the operating
area is determined by the higher hazard storage.
For example, the operating area is 2500 ft2 (232 m2). The
system must be able to provide the 0.3 gpm/ft2 (12.2 mm/
min) density over the storage area and 15 ft (4.57 m) beyond.
If part of the remote area is outside the 600 ft2 (55.7 m2) plus
the 15 ft (4.57 m) overlap, only 0.2 gpm/ft2 (8.1 mm/min) is
needed for that portion.
If the storage is separated from the surrounding area by a
floor-to-ceiling/roof partition that is capable of preventing
heat from a fire on one side from fusing sprinklers on the
other side, the size of the operating area is determined by the
occupancy of the surrounding area. In this example, the design
area is 1500 ft2 (139 m2). A 0.3 gpm/ft2 (12.2 mm/min)
density is needed within the separated area with 0.2 gpm/ft2
(8.1 mm/min) in the remainder of the remote area.
Thank you,
Ryan L. Hinson, EIT, NICET III
Fire Protection Engineer, Aviation & Facilities Group
Burns & McDonnell
Minneapolis-St. Paul Office
8201 Norman Center Drive, Suite 300
Bloomington, MN 55437
Direct: 952-656-6003 Ext 3662
Fax: 952-229-2923
[email protected]
www.burnsmcd.com<BLOCKED::www.burnsmcd.com>
Proud recipient of PSMJ's Premier Award for Client Satisfaction
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