7. LIMITATIONS OF SMOKE ALARMS
WARNING: PLEASE READ CAREFULLY AND THOROUGHLY
•  NFPA 72 states: Life safety from fire in residential occupancies 
is based primarily on early notification to occupants of the need 
to escape, followed by the appropriate egress actions by those 
occupants. Fire warning systems for dwelling units are capable 
of protecting about half of the occupants in potentially fatal 
fires.  Victims are often intimate with the fire, too old or young, 
or physically or mentally impaired such that they cannot escape 
even when warned early enough that escape should be possible. 
For these people, other strategies such as protection-in-place or 
assisted escape or rescue are necessary.
•  Smoke alarms are devices that can provide early warning of pos-
sible fires at a reasonable cost; however, alarms have sensing 
limitations. Ionization sensing alarms may detect invisible fire 
particles (associated with fast flaming fires) sooner than photo-
electric alarms. Photoelectric sensing alarms may detect visible 
fire particles (associated with slow smoldering fires) sooner than 
ionization alarms.  Home fires develop in different ways and are 
often unpredictable. For maximum protection, Kidde recom-
mends that both Ionization and Photoelectric alarms be installed.
•  A battery powered alarm must have a battery of the specified type, 
in good condition and installed properly.
•  AC powered alarms (without battery backup) will not operate if 
the AC power has been cut off, such as by an electrical fire or 
an open fuse.
•  Smoke alarms must be tested regularly to make sure the batter-
ies and the alarm circuits are in good operating condition.
•  Smoke alarms cannot provide an alarm if smoke does not reach 
the alarm.  Therefore, smoke alarms may not sense fires starting 
in chimneys, walls, on roofs, on the other side of a closed door 
or on a different floor.
•  If the alarm is located outside the bedroom or on a different 
floor, it may not wake up a sound sleeper.
•  The use of alcohol or drugs may also impair one’s ability to hear 
the smoke alarm.  For maximum protection, a smoke alarm 
should be installed in each sleeping area on every level of a 
home.
•  Although smoke alarms can help save lives by providing an early 
warning of a fire, they are not a substitute for an insurance 
policy.  Home owners and renters should have adequate insur-
ance to protect their lives and property.
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