Slides 20 and 21
Here is an interesting piece of information. Here is what NIST disclosed to the Boston City Council during the period when the state of Massachusetts was examining photoelectric legislation. NIST testified that,
“ionization alarms may not always alarm, even when a room is filled with smoke from smoldering fire”
and that ionization alarms are a little faster (i.e. up to 30 seconds) in a flaming fire and that photoelectric provide a lot more time in a smoldering fire (i.e. over a half of an hour).
Also remember which fire kills the most people.
NIST went on to also point out the problems of with the ionization’s nuisance alarm problems.
So why doesn’t NIST make this information readily available to Fire Chiefs/the fire industry?
(c) Copyright July 09
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National Institute of Standards and Technology
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to the Boston City Council Committee on Public Safety
Statement for the Record - August 6, 2007 -
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In summary, the research conducted by NIST staff leads to the conclusion that both ionization and photoelectric alarms provide enough time to save lives for most of the population under many fire scenarios; however, ionization alarms may not always alarm even when a room is filled with smoke from a smoldering fire, exposing the most sensitive populations with mobility limitations to an undetermined risk.
Photoelectric detectors can provide a lot more warning time than ionization detectors in a smoldering fire; at the same time a smoldering fires can take a longer period to become dangerous. Ionization detectors can provide a little more time than photoelectric detectors in a flaming fire; in this case there can be little time to spare. Changes in furnishing materials and construction over the past decades have reduced the time available for safe egress in any fire. NIST is currently conducting research to assess whether or not modifications may be needed in the standard test method for certifying residential smoke alarms to accommodate the changing threat.
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