sprinklernotes
Localized Protection
You asked the following question: “A noncombustible concealed space within an
airport has noncombustible platforms within it and there are conveyors above
the platforms. Consequently, the concealed space is fully sprinklered. The
space below the platform to the ceiling varies but is as much as 6 ft in
height. There are no combustibles below the platform, and there is no ability
to store below the platform as there is nothing below it but noncombustible
ceiling, duct, lighting and those items typically found above the ceiling in a
noncombustible concealed space. The question is, should the platform itself be
considered an obstruction requiring sprinklers below it, or is it not an
obstruction because there is no hazard below the platform?”
In response to your question, we have reviewed NFPA 13, Standard for the
Installation of Sprinkler Systems, 2010 edition. Our informal interpretation is
that because the space is fully sprinklered, sprinklers would be required to
meet the obstruction rules of NFPA 13.
An argument could be made that sprinklers would only be required to protect the
localized hazard per section 8.15.1.5(2):
8.15.1.5 Localized Protection of Exposed Combustible Construction or Exposed
Combustibles. When otherwise noncombustible or limited-combustible concealed
spaces that would not require sprinkler protection have localized exposed
combustible construction, or contain localized areas of exposed combustibles,
the combustibles shall be permitted to be protected as follows:
(1) If the exposed combustibles are in the vertical partitions or walls around
all or a portion of the enclosure, a single row of sprinklers spaced not over
12 ft (3.7 m) apart nor more than 6 ft (1.8 m) from the inside of the partition
shall be permitted to protect the surface. The first and last sprinklers in
such a row shall not be over 5 ft (1.5 m) from the ends of the partitions.
(2) If the exposed combustibles are in the horizontal plane, the area of the
combustibles shall be permitted to be protected with sprinklers on a light
hazard spacing. Additional sprinklers shall be installed no more than 6 ft (1.8
m) outside the outline of the area and not more than 12 ft (3.7 m) on center
along the outline. When the outline returns to a wall or other obstruction, the
last sprinkler shall not be more than 6 ft (1.8 m) from the wall or obstruction.
However, since the space is already fully sprinklered, the entire space must
comply with all of the requirements of NFPA 13. For standard uprights and
pendants, if the conveyors are within 18 in. of the deflector, sprinklers must
be spaced and positioned to meet the beam rule and three times rule. If the
conveyors are more than 18-in. below the deflector, then sprinklers must be
installed below obstructions over 4 ft in width.
