Table 3 Follow-up status of study smoke alarms, by follow-up visit and alarm type
CharacteristicFollow-up 1Follow-up 2Follow-up 2*
Ionization (n = 332) (%)Photoelectric (n = 340) (%)p-value†Ionization (n = 311) (%)Photoelectric (n = 314) (%)p-value†Ionization (n = 248) (%)Photoelectric (n = 296) (%)p-value†
Participant-reported status since last visit
Study alarm sounded77.938.7<0.00176.842.0<0.00174.241.8<0.001
No. of times study alarm sounded‡<0.001<0.001<0.001
Other alarm(s) sounded§42.545.40.4933.037.60.2630.236.70.14
No. of times other alarm(s) sounded‡0.890.280.07
Observed status of study alarm
Non-functional due to
    Malfunctioning alarm0.30.00.490.
    Disconnected battery5.80.6<0.0015.51.30.0044.10.70.008
    Absent battery12.81.2<0.00114.52.2<0.0017.72.40.004
    Dead battery0.91.50.731.
    Incorrect battery placement0.
Study alarm removed0.
  • *Restricted to households with functional study alarms at follow-up 1.

  • †Based on Pearson’s χ2 test if expected ⩾5 in all cells; based on Fisher’s exact test if expected <5 in any cell.

  • ‡Restricted to households whose smoke alarm(s) had alarmed since the last visit.

  • §Restricted to households with reported non-study alarms at baseline.