1. #1
    Forum Member

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    Nov 2002

    Default Flawed smoke detectors

    Compare these 2 statements.

    From “Fatal Fires” Topical Research Series Vol. 5 – Issue 1, USFA March 2005.

    “Smoke alarms were present in 58% of fatal residential structure fires, but only operational in 37% of those fatal fires.”

    In this report the USFA meant the following:

    · No Detector Present – 43%
    · Detector Present and operated – 37%
    · Detector Present and did not Operate – 21%

    From “Fatal Fires with Operational Smoke Alarms” Topical Research Series Vol. 6 – Issue 2, USFA August 2006.

    “Alarms were present in 60% of fatal residential structure fires. Of those fatal fires with an alarm present, the detector operated 39% of the time. Together these statistics indicate that alarms were present and operated in 23% of fatal residential structure fires.”

    The first 2 sentences, of this claim are very similar to the previous claim but in this report the third sentence provides a new and very different analysis. In this report the USFA appears to mean the following:

    · No Detector Present – 40%
    · Detector Present and operated – 23%
    · Detector Present and did not Operate – 37%

    Therefore, according to the USFA, from March of 2005 to August of 2006, the % of fatalities that occurred with an operating detector went from 37% down to 23%. While simultaneously, the % of fatalities that occurred with a detector that did not operate went from 21% to 37%. This makes no sense. I suspect that the author of this report mistakenly multiplied the 60% by 39% instead of leaving the 39% alone.

    I suppose this could be due to a grammatical error except for the fact that it varied so much from previous estimates. Here is a summary of statistics from previous USFA Reports titled “Fire in the U.S.” Increase in fatal fires with working detectors – 1988 (9%), 1994 (19%), 1996 (21%), 1998 (29%), 2001 (39%). While there will always be a certain percentage of people who cannot be saved by smoke detectors, e.g. the handicapped, those intimate with the fire etc., there is no reason to believe that the number of those people quadrupled between 1988 and 2001. In addition, while the number of fires with working detectors increase approximately in proportion to the increase in the number of detectors installed, the increase in the % of fatal fires with working detectors far exceeds it.

    In my opinion the best explanation is that starting in the late 80’s, Underwriters Labs, in an attempt to reduce nuisance alarms, forced the manufacturers to make less sensitive ionization detectors. Shortly after this change UL modified the smoldering test in UL217, the UL Smoke Detector Standard, in ways that made it much easier for the ionization detector to pass. The gradual introduction of these desensitized ionization detectors into American homes is the most reasonable explanation for the increase in fire deaths in cases where the detector operated. As a consequence this unrecognized flaw could be responsible for hundreds of deaths per year.

    Another problem not really investigated by the Report is the number of fatalities that occur when the detector is disabled. Even if I am correct that the number of fatalities occurring when the detector is disabled is approximately 20% and not 37%, it is still a significant problem. If that is the case why does the USFA state, “Some models sound false alarms when they detect cooking smoke…” Why not point out that the models they are referring to are ionization detectors. Here is a quote from a recent study in Alaska.

    ”In this study they found that at the end of 6 months 19% of the homes with ionization detectors had disabled the detector and over 80% of the time the reason was that “it goes off too much” with 93% of the false alarms related to cooking. Only 4% of the photoelectric detectors were disables and none of the reasons were related to nuisance alarms.” (Ionization and photoelectric smoke alarms in rural Alaskan homes”, Alaska Injury Prevention Center, August 2000)

    The USFA report recommends, “relocating alarms farther from sources of fumes,” but what is someone to do in a small apartment or mobile home. Since HUD allows ionization detectors to be installed in mobile homes, where the layout guarantees they will be near a kitchen, we would expect to see a problem and we do. According to the USFA over 80% of the fatalities in mobile homes, where the operation of the detector is known, occurred when the detector was disabled. Why blame the victims in these cases? Why isn’t HUD mandating photoelectric detectors for mobile homes? Why isn’t the USFA sharing this information with the public?


    More informatin can be found by looking up a paper I wrote that is available at interfire.org. (Search on Detectors.)

  2. #2
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    May 2004


    You Have To Much Time On Your Hands.

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