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.
