Performance of Home Smoke Alarms - National Institute of ...

On average, the photoelectric alarms provided positive available egress time for allmanufactured home fire scenarios, with available safe egress times ranging from 58 s to 2234 s.Ionization type alarms, on average, provided positive escape times for all tested fire scenariosexcept the smoldering chair (ranging from -43 s to 1036 s). The ionization alarms did not,however, provide positive available egress time in every test for the smoldering chair scenarioswhen the alarms were located on every level. On average, dual mode alarms using both thephotoelectric and ionization principles provided positive escape times except for the flamingmattress (ranging from –10 s to 1445 s). It is interesting to note that the dual-mode alarmsprovided a typically slower response than ionization alarms to flaming fires; likely due to a morecomplex design of the dual-mode alarm. Ionization type smoke alarms provided the longestegress times for flaming (and grease) fires and photoelectric smoke alarms provided the longestescape times for smoldering fires. Similar trends are seen for the two-story home tests, withionization alarms providing the longest egress times for flaming fires.As expected, alarm placement can effect the available safe egress time. For the manufacturedhome tests, including alarms in bedrooms or in every room in addition to those on every levelincreases average available safe egress time by 3 s to 1300 s, depending upon fire scenario,alarm type, and alarm placement. Greater increases are noted for photoelectric (up to 1304 s) ordual photoelectric / ionization alarms (up to 923 s) than for the ionization alarms (up to 293 s).The change from every level placement to every level + bedrooms provided the greatest typicalincrease, averaging 294 s, 64 s, and 329 s additional egress time for the photoelectric, ionization,and dual photoelectric / ionization alarms, respectively. No increase was seen for the aspiratedphotoelectric detector. This may be due to the periodic sampling of this detector. For the twostoryhome tests, the effect was far less pronounced. This is likely due to the interior design ofthe home. For fires downstairs, the upstairs hallway alarms were typically the first to respondsince there was not soffit to impede smoke flow from the first floor into the stairwell to thealarms at the top of the stairs.241