One outside each sleeping area, one each bedroom, one each floor. Not in kitchen or bathrooms. I center mine on bedroom doors, about two foot into the room. Instructions with detectors will help if you take the time to read them. Local ordinances may have a suggestion or two.Just as the title states. look for a quick reference guide on laying out smoke detectors.
Not for 2010 and later editions of NFPA 72. If you have an irregular space, the technical coverage for a smoke detector is a 21 foot radius circle. Inside that will fit (almost) a 30' square, hence the allowed default spacing.Detector Layout:
W = Width of the area
S = Listed spacing of detector
D = Number of Detectors required ANY remainder rounds D to the next higher number
A = Adjusted spacing Applies asthetics to the installation
H = Sidewall spacing A Sidewall was used to measure W
D = W / S
A = W / D
H = A / 2
To check your work, use a scale drawing of your layout:
Set a compass to 0.7 times scaled S;
Swing a circle around each detector location;
If the entire area is contained by one or more circles, you meet code.
Can be used for both smoke and heat detectors but not projected beam detectors. If heat detectors are mounted more than 10', up to 30' AFF, apply "height derating percentage" before using the above.
Smoke Detector specifics:
Ceiling Mounted -- No part of the detector within 4" of a wall.
Wall Mounted -- Some part of the detector within 12" of the ceiling but no part of the detector within 4" of the ceiling.
Not within 3' of an air outlet.