Institute of Standards and Technology
(NIST) is a federal technology agency that develops and promotes
measurement, standards, and technology. In
issued a comprehensive report entitled Performance
of Home Smoke Alarms — Analysis of the Response of Several
in Residential Fire
The report concludes, among other things, that "smoke alarms of
either the ionization type or the photoelectric type consistently
provided time for occupants to escape from most residential fires",
and "consistent with prior findings, ionization type alarms
provided somewhat better response to flaming fires than photoelectric
alarms, and photoelectric alarms provided (often) considerably faster
response to smoldering fires than ionization type alarms”. Optical
or "toast-proof" smoke detectors are generally quicker in
detecting particulate (smoke) generated by smoldering (cool, smokey)
fires. Ionization smoke detectors are generally quicker in detecting
particulate (smoke) generated by flaming (hot) fires.
The NFPA strongly recommends the replacement of home smoke alarms every 10 years. Smoke alarms become less reliable with time, primarily due to aging of their electronic components, making them susceptible to nuisance false alarms. In ionization type alarms, decay of the Am radioactive source is a negligible factor, as its half-life is far greater than the expected useful life of the alarm unit.
Regular cleaning can prevent false alarms caused by the build up of dust or other objects such as flies, particularly on optical type alarms as they are more susceptible to these factors. A vacuum cleaner can be used to clean ionization and optical detectors externally and internally. However, on commercial ionization detectors it is not recommended for a lay person to clean internally. To reduce false alarms caused by cooking fumes, use an optical or 'toast proof' alarm near the kitchen.