Potter Fire Alarm Systems - Manual (Page 17)

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Fire Alarm Training • 8700055 • Rev F • 4/10
For areas with smooth and flat ceilings that are ten feet in height or lower:
• A spacing of 30 feet shall be permitted as a guide for smoke detector placement. Smoke detectors do not have a listed spacing.
• All points on the ceiling shall have a detector within a distance equal to .7 times the selected spacing.
• Spot type detectors shall be located on the ceiling not less than four inches from a side wall or, if mounted on a side wall,
between four and twelve inches down from the ceiling to the top of the detector.
• The distance between detectors shall not exceed their selected spacing. There shall be detectors within one-half the selected
spacing, measured at right angles, from any side wall.
• Detectors shall not be recessed mounted unless specifically listed for recess mounting.
• Spot type smoke detectors must be a minimum 36” from air diffusers, and may not be in a direct airflow exceeding their air
velocity, regardless of distance.
• Detectors shall be supported independently of their attachment to circuit conductors.
• Spot type detectors should be mounted at least 6” from florescent lights.
• Except in cases where “stratification” is expected, detectors shall never be mounted more than 12” below ceiling level.
DWG# 55-3
Rectangles
A = 10’ x 41’
B = 15’ x 39’
C = 20’ x 37’
D = 30’ x 30’
A A B
B
C C
D D
If 30 feet is used as a guide, any square that will fit inside of a circle with a 21foot radius could be covered with a single smoke detector.
Note that an area 10ft. by 41ft. can be covered by one smoke detector using 30ft. spacing.
Smooth Ceiling Spacing - Spot type Smoke Detectors
Spacing of 30 feet may be used as a guide, consult manufacturers instructions.
NFPA72, 2007 5.7.3.2.3.1
Solid Joist and Beam Construction
Solid joists shall be considered equivalent to beams for smoke detector placement.
NFPA72 2007, 5.7.3.2.4.1