Simplex 4098 Applications Manual page 9

WHERE TO PLACE DETECTORS/SENSORS, Continued
Detectors/sensors may also be omitted from below open grid ceilings where all
of the following conditions are met:
•
The openings of the grid are at least 1/4 inch (6 mm) in the smallest
dimension.
•
The thickness of the material does not exceed the smallest of the grid
openings.
•
The openings constitute at least 70% of the area of the ceiling material.
Detectors/sensors are usually required or recommended underneath open loading
docks or platforms and their covers, and in accessible underfloor areas in
buildings without basements. Detectors/sensors may be omitted from
combustible blind spaces when all of the following conditions prevail:
1. The space is not accessible for storage purposes, it is protected against the
entrance of unauthorized persons, and it is protected against the
accumulation of windblown debris.
2. The space contains no equipment/structures (such as steam pipes, electrical
wiring, ducts, shafts, or conveyors) that could potentially ignite or conduct
the spread of fire.
3. The floor over the space is tight.
4. Non flammable liquids are processed, handled, or stored on the floor above
the space.
"Total coverage," as described in NFPA 72, is the definition of a complete fire
detection system. In some of the specified areas of coverage, such as attics, closets,
under open loading docks or platforms, a heat detector may be more appropriate
than a smoke detector. Careful consideration should be given to the detector
manufacturer's instructions and the following recommendations in this guide.
3
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