Smoke alarms are the cheapest, simplest life-safety device in your home, and they're also one of the most commonly overlooked items until an inspection turns up a problem.
California requires interconnected smoke alarms in every bedroom, outside each sleeping area, and on every level of the home, including basements. "Interconnected" means when one sounds, they all sound, whether that's hardwired or newer wireless-linked units.
Alarms have a shelf life. Most manufacturers rate them for 10 years from the manufacture date — or 7 years for combo smoke/carbon-monoxide alarms — printed on the back of the unit, not the install date. Past that, the sensor degrades even if the alarm still beeps during a test.
The stakes are real: nearly 59% of home fire deaths happen in properties with no smoke alarms, and another 43% occur because the alarms failed to operate. And remember what the device is actually for — smoke detectors aren't meant to detect fire so much as to wake you if you're sleeping when fire or heavy smoke arises.
Why does the smoke alarm always chirp at night?
Smoke alarms warn you when the battery gets low by "chirping" — and lower temperatures slow the chemical reaction inside a battery. A battery nearing the end of its life might power the alarm just fine during warmer daytime hours, but when the cooler evening hits, its power output drops below the threshold. That's when the detector chimes in — which is why it always seems to wake you in the dead of night with that annoying CHIRP.
Smoke detector vs. smoke alarm
Technically, a smoke detector senses smoke and sends a signal to a central alarm system, whereas a smoke alarm includes a built-in audible and/or visible alert. Both terms get used interchangeably for the devices in our homes.
Where they go — and where they can't
Smoke alarms shall be installed in each sleeping room, outside each separate sleeping area in the immediate vicinity of the bedrooms, and on each level of the home including basements and habitable attics. If the house has separate hallways leading to separate bedroom groups, each hallway gets its own alarm.
The installation standards also say where they can't go: not within 3 feet of the door of a bathroom containing a tub or shower, not within 3 feet of an HVAC supply register, not within 3 feet of the blade tip of a ceiling fan, and a minimum of 20 feet from a cooking appliance. On coffered ceilings, detectors go on the highest portion of the ceiling or on the slope within 12 inches vertically of the highest point.
What about carbon monoxide alarms?
California's SB-183 requires a carbon monoxide device in all dwelling units intended for human occupancy. CO is a colorless, odorless gas produced by heaters, fireplaces, furnaces, and many appliances and cooking devices. CO devices should be installed outside each sleeping area of the home including the basement, with one device per habitable level that has a fuel-burning appliance — and always per the manufacturer's installation instructions.
During a home inspection, we test each unit, check placement against these standards, and verify interconnection. It's a small line item on the report, but it's one of the easiest fixes to knock out before move-in.