Wireless interconnected smoke alarms: what to know before buying
Updated
When one alarm senses smoke, every alarm in the house sounds. Here is where to put them, why brands usually cannot be mixed and when a hardwired system needs an electrician.
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What “interconnected” means
A single stand-alone alarm only protects the room it is in. If a fire starts in the garage or basement while you sleep two floors up, you may not hear it until the smoke reaches you. Interconnected alarms fix this: when one detects smoke, all of them sound. The U.S. Fire Administration (USFA) puts it simply: choose interconnected alarms so that when one sounds, they all sound.
There are two ways to link alarms. Hardwired alarms run on house wiring (120 V) and are linked by a wire between them, usually with a battery backup. Wireless alarms run on batteries, commonly a sealed 10-year lithium cell, and link by a built-in radio. Wireless is the practical choice for renters, older homes with plaster ceilings and anyone who does not want to run new cable.
How many alarms and where
USFA’s advice is to put smoke alarms inside and outside each bedroom and sleeping area, and on every level of the home, including the basement. Mount them on the ceiling or high on a wall and follow the maker’s instructions for the exact spot.
| Home | Typical spots | Alarms |
|---|---|---|
| One-bedroom apartment | Bedroom, hallway or living area outside the bedroom | 2 |
| Two-story, 3 bedrooms, no basement | 3 bedrooms, upstairs hallway, ground floor living area | 5 |
| Two-story, 3 bedrooms, finished basement | 3 bedrooms, upstairs hallway, ground floor, basement | 6 |
| Ranch with attic or garage entry | Each bedroom, hallway, living area; extra near the door to the garage if the maker allows | 5 or more |
Keep alarms away from the kitchen stove and the bathroom to limit false alarms; see smoke alarm near the kitchen for distances and fixes.
Why you cannot mix brands
Wireless interconnect uses the maker’s own radio language. Alarms from one product family link to each other; alarms from different families generally do not, even when both say “wireless”. Check the box for the exact model numbers the alarm links with. If you already own alarms that do not link, you have two options: replace them with a single family, or add a smoke alarm listener to the old ones (see smart smoke alarm vs listener).
Also do not confuse two features. Interconnect makes alarms in the house sound together. Smart alerts send a notification to your phone over Wi-Fi or a hub. Some alarms do both, some only one. If your phone alert is the only thing you rely on and the Wi-Fi is down, the local sirens still must work, so look for alarms that interconnect on their own radio.
Which sensor type to look for
USFA recommends either both ionization and photoelectric alarms, or dual-sensor alarms, in every home and sleeping area. Look for a listing to the UL 217 standard, which UL Solutions describes as covering smoke alarms.
Hardwired alarms and the 120 V line
USFA says only qualified electricians should install hardwired smoke alarms. If your ceiling already has hardwired alarms, you can usually replace them with a compatible model of the same family, with power off at the breaker, but wiring changes, new locations or extra hardwired units are a job for a licensed electrician who follows local code. Hardwired alarms from different makers also often use different plugs. When in doubt, do not mix.
Batteries, testing and the 10-year rule
- Test monthly. USFA says to test every alarm monthly; on interconnected alarms, pressing one test button should sound all of them.
- Replace the whole alarm 10 years after the manufacture date. The date is printed on the back. USFA notes that long-life lithium alarms have non-replaceable batteries, so you replace the unit.
- Replace 9-volt batteries at least once a year in alarms that use them, and hardwired backup batteries once a year.
- Never take out the battery. A dead or missing battery means the alarm is effectively absent.
Renters, older adults and people who cannot hear the alarm
Renters: battery-powered wireless alarms need no wiring, but check your lease and ask the landlord before replacing alarms the landlord supplied, and never remove one. Rules on who must provide and maintain alarms vary by state and city; ask a local tenant organization if unsure. For anyone who is deaf or hard of hearing, or sleeps deeply, USFA notes that some alarms have strobe lights and vibration; see the visual and vibrating alert kit. A complete setup with carbon monoxide protection is in the smart smoke and CO alarm kit.
Cost
USFA lists radio-frequency (wireless) alarms from about $40. Expect roughly $30–$80 for a battery-powered smoke alarm that links wirelessly and $45–$120 for a smoke and CO combination. A six-alarm home therefore costs about $180–$480 in alarms. Some local fire departments offer free or reduced-price alarms, so ask yours.
Shop by need
Renter who cannot touch the wiring
What to look for: battery-powered, 10-year sealed lithium cell, wireless interconnect, photoelectric or dual-sensor, UL 217 listing, hush button
Typical price: $30–$80
See options on AmazonHomeowner who wants smoke and CO on each level
What to look for: smoke and CO combination, wireless interconnect with the same family, voice location callout, UL 217 and UL 2034 listings
Typical price: $45–$120
See options on AmazonHome with existing hardwired alarms
What to look for: replacement from the same family as the existing alarms, matching plug harness, battery backup, installation by an electrician if wiring changes
Typical price: $25–$70
See options on AmazonPerson who is deaf or hard of hearing
What to look for: strobe light, bed shaker or pillow vibrator that links to the alarms, low-frequency sounder
Typical price: $50–$160
See options on AmazonFrequently asked questions
Can I mix smoke alarm brands and still have them interconnect?
Usually not. Wireless alarms link through the maker’s own radio protocol, so use one product family throughout. The packaging lists the model numbers each alarm links with.
How many wireless smoke alarms do I need?
The U.S. Fire Administration says to put them inside and outside each bedroom and sleeping area and on every level, including the basement. A two-story home with three bedrooms and a basement typically needs about six.
Do wireless smoke alarms work if the Wi-Fi is down?
The interconnect between alarms uses its own radio, so the alarms should still sound together. Phone notifications need the internet.
How often should I replace interconnected smoke alarms?
The U.S. Fire Administration says 10 years from the manufacture date printed on the alarm. Test them monthly.