Although smoke alarms with lithium batteries are often marketed as ‘10-year alarms’, on average, these alarms do not remain functional for 10 years. This paper describes self-reported reasons for non-working lithium-battery alarms 6–9 months following a smoke alarm installation programme. Data presented are for a cohort of 754 homes that participated in the installation programme and subsequently completed follow-up. A total of 1487 smoke alarms were installed. At follow-up, 126 alarms (8%) were missing and 37 (3%) were observed to be non-working. Of the non-working alarms, residents reported that they had been disabled 57% of the time. Reasons for disabling the alarms most often included that the battery was chirping (38%) or that it sounded while someone was cooking (24%). Smoke alarm installation programmes using lithium-battery alarms should consider highlighting education about smoke alarm maintenance, the hush feature and resources to replace alarms that malfunction soon after installation.