Smoke detector

A smoke detector, also known as a fire alarm, is an electronic device in The Sims, The Sims 2, The Sims 3, and The Sims 4. It alerts Sims and the Fire Department when there is a fire in the house. This is a useful item because Sims often have an autonomous reaction to go see a fire and won't phone the Fire Department or extinguish it themselves even if directed.

The fire alarm will only work if it is in the same room as the fire. For example, if there is an oven that is on fire and one fire alarm up in the bedroom, it will not work.

The Sims
The Sims introduced a smoke detector that automatically phoned the fire department when a fire broke out in the same room as the detector. The detector covers all tiles in the room it is placed in. If placed outdoors, it will cover the entire outdoor area, limited only by fences.

The Sims 2
The Sims 2 introduced a smoke detector that worked similarly to the one in The Sims. A firefighter from the fire department will arrive almost immediately after the alarm goes off, and the noise will alert other Sims around the lot to the fire. If placed outdoors, it will cover the entire outdoor area, limited only by fences.

The Sims 3
Fire alarms in The Sims 3 work similarly to the ones in previous generations. They will automatically summon the fire department if a fire breaks out in the same room, and will cover the entire outdoor area—limited only by fences—if placed outdoors.

The Sims 4
In The Sims 4, all fire alarms on the same floor regardless if separated by rooms will activate immediately after a fire has started. Fire alarms that have been placed upstairs, however, will not react to a fire. As of Update 06/03/2020, firefighter NPCs have been added and will automatically come to the lot when a smoke alarm detects a fire. If the Fire Prevention System Utility Panel is present on the lot, smoke alarms will trigger sprinklers to appear over the fire and extinguish it.