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(c) Copyright July 09

    1. Statement for the Record - August 6, 2007

    2. National Institute of Standards and Technology

    3. to the Boston City Council Committee on Public Safety


    5. continued . . .

    6. In NIST's smoke alarm research, and in applications in the field, it is documented that most
      common ionization detectors have a propensity to produce nuisance alarms during cooking
      activities. NIST examined a broad range of activities (including cooking) that yield nuisance
      alarms. The published field observations guided the nuisance alarm scenarios studied.
      Specifically, the sensitivity to alarm threshold, distance from the source, background air flows, and alarm sensor (photoelectric or ionization) were examined.  Additional measurements were made with aerosol instrumentation to provide a more fundamental understanding of nuisance alarm sources than has been previously published. Given the scenarios examined, both photoelectric and ionization alarms produced nuisance alarms, but NIST does not mean to imply that they are equally susceptible to such nuisance alarms.
      Most field data suggest that ionization alarms have a greater propensity to nuisance alarm than photoelectric alarms, possibly indicating that certain activities such as cooking dominate reported nuisance alarms in the field.

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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 a 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?