Smoke alarms by type and battery life in rural households: a randomized controlled trial.

Background: Although the use of smoke alarms is widely recommended, little guidance is available on the types of alarms and batteries that function best. This study examined smoke alarm and battery function 12 months after installation in rural residential households.

Methods: An RCT, involving the installation of either a photoelectric or ionizing smoke alarm with either a lithium or carbon-zinc battery, was conducted in 643 rural Iowa households in July 2003. The functionality of each installed smoke alarm was tested 12 months later. Generalized estimating equations were used to model the effects of alarm type and battery type on alarm function and false alarms 12 months after installation.

Results: Of 643 study homes, 98.8% had at least one functioning alarm, and 81.5% had all alarms functioning 12 months after installation. No difference was observed in alarm function between photoelectric alarms and ionizing alarms 12 months after installation (OR=1.30, 95% CI=0.88, 1.92). However, photoelectric alarms had significantly lower odds of false alarms than ionizing alarms. Alarms with lithium batteries had 91% higher odds of functioning than those with carbon-zinc batteries. The main reasons for nonfunctioning included a missing battery (30.7%); a missing alarm (28%); and a disconnected battery (11.3%).

Conclusions: Although lithium batteries and photoelectric alarms are more expensive than their counterparts, the financial investment might be worthwhile in terms of overall performance.