Smoke alarm and battery function 42 months after installation: a randomized trial.

Background: This randomized trial presents findings from the longest follow-up study of smoke alarm and battery function to date.

Purpose: The purpose of this study is to examine differences in long-term function of smoke alarm and battery combinations.

Methods: A total of 691 households in an ongoing cohort study were randomly allocated into smoke alarm groups of ionizing and photoelectric and battery groups of zinc and lithium. Smoke alarm function was measured in 633 (91.6%) households from January 2007 through February 2008, 42 months following original smoke alarm/battery installation. Data analyses were conducted in 2009.

Results: After 3.5 years, 81.9% of the 1898 smoke alarms were functional. Ionizing alarms with zinc batteries were the least likely to function (72.7%). In comparison, photoelectric alarms with lithium batteries were 2.9 times (95% CI=1.8, 4.5) more likely to function; ionizing alarms with lithium batteries were 2.0 times (95% CI=1.3, 3.1) more likely to function; and photoelectric alarms with zinc batteries were 1.7 times (95% CI=1.1, 2.5) more likely to function. Functionality was strongly tied to number of reports of nuisance alarms, which was higher for ionizing than photoelectric alarms.

Conclusions: Photoelectric smoke alarms and lithium batteries are the most likely to function long after smoke alarm installation, and may be worthwhile investments despite their increased cost.