Determine how many smoke detectors your home needs by floor.
The modern residential rule is one smoke alarm inside every bedroom, one outside each sleeping area in the hallway or on the landing, and one on every level including the basement. That is a bigger number than most houses actually have: a three-bedroom two-storey home with a basement needs six. The inside-bedroom requirement is the one most often missing in older properties, and it matters because a closed bedroom door delays a hallway alarm long enough to change the outcome. Interconnection matters as much as count — when a basement alarm sounds, the bedroom alarms should sound too, which is why hard-wired or wirelessly linked alarms outperform the same number of standalone units.
Smoke Detector Count
Alarms = one per bedroom + max(hallways, storeys) for circulation + 1 for a basement
Fire safety is governed by local building and housing codes, and requirements for interconnection, power source and alarm type differ by jurisdiction and tenancy status. Treat this as planning guidance and confirm with your local fire authority or building official.
Under current codes, yes. A closed door blocks smoke long enough that a hallway alarm alone may not wake a sleeper before conditions in the room become dangerous.
Every ten years from the date stamped inside, regardless of whether they still test. The sensing chamber degrades with dust and age, and the test button only checks the horn and power.