Smoke and Carbon Monoxide Alarms: Where They Go and When to Replace Them

Put a smoke alarm inside every bedroom, outside each sleeping area, and on every level of the home, including the basement — on the ceiling or high on a wall, at least 10 feet from the stove. Put carbon monoxide (CO) alarms in a central spot outside each sleeping area and on every level too. Test every alarm monthly, replace smoke alarms 10 years from their manufacture date, and replace CO alarms on the schedule printed on the unit. As of September 2026, that's the guidance from the National Fire Protection Association (NFPA) and the U.S. Fire Administration (USFA).

Where should smoke alarms go?

• Inside every bedroom.
• Outside each separate sleeping area, such as the hallway it opens onto.
• On every level of the home, including the basement.
• On the ceiling or high on a wall — never in the kitchen or bathroom, where steam and cooking smoke cause false alarms. NFPA says to keep alarms at least 10 feet from the stove.
• Interconnected where possible, so that when one sounds, they all sound.

Source: NFPA, "Smoke alarms", as of September 2026.

Battery-powered and plug-in alarms can go up without an electrician. Hardwired smoke alarms are different: NFPA says only a qualified electrician should install them, since they tie into the home's wiring. Don't attempt that wiring yourself; book smoke and carbon monoxide detector installation instead.

Where should carbon monoxide alarms go?

CO alarms go in a central location outside each sleeping area, on every level of the home. Follow the manufacturer's instructions for exact mounting height. Interconnected CO alarms, like interconnected smoke alarms, all sound together when one detects gas.

Source: NFPA, "Carbon monoxide", as of September 2026.

If a CO alarm sounds: get everyone to fresh air right away — outdoors, or to an open window or door — account for every person in the home, and call for help from there. Don't go back in to investigate.

How often should you test smoke and CO alarms?

Test every alarm once a month. Push the test button and listen for the alarm tone; that's the only way to know a unit is actually working. This applies to both smoke and CO alarms, per NFPA and the U.S. Fire Administration.

When should you replace smoke and carbon monoxide alarms?

The 10-year figure for smoke alarms is counted from the date of manufacture, printed on the back of the unit — not from when you bought it or moved in. If you don't know when a smoke alarm was installed, check that date before assuming it's still good.

CO alarms don't have a single fixed replacement age the way smoke alarms do. NFPA's own guidance is to replace a CO alarm "according to the manufacturer's instructions," so check the date printed on your unit rather than assuming a set number of years.

Source: NFPA and USFA, as of September 2026.

What does Virginia law require for smoke and CO alarms?

Virginia's rules split between a general accommodation statute and the landlord–tenant law for rentals. As of September 2026:

• § 36-99.5 is not a general smoke-alarm law. It requires a landlord to provide a smoke alarm for a deaf or hard-of-hearing tenant, on request, and lets the landlord charge a refundable deposit for it. It doesn't set placement or replacement rules for every home. (Va. Code § 36-99.5)
• Rental units, smoke alarms: under the Virginia Residential Landlord and Tenant Act, a landlord must give the tenant a certificate that all smoke alarms "are present, have been inspected, and are in good working order," and this certificate need be given "no more than once every 12 months" — that wording limits how often the certificate is required, not how often the alarms must be inspected in some other sense. (Va. Code § 55.1-1220 A 8) Tenants, in turn, must not remove or disable a working smoke alarm, including taking out its batteries, and must maintain it. (Va. Code § 55.1-1227 A 8)
• Rental units, CO alarms: the landlord has no automatic duty to install one, but must install a CO alarm within 90 days of a tenant's written request, and may charge a reasonable fee for the equipment and labor. (Va. Code § 55.1-1229 E) A tenant must not disable a CO alarm the landlord installed. (§ 55.1-1227 A 9)

This is general information, not legal advice; confirm anything specific to your lease with your landlord or the office that administers it.

Why do smoke and CO alarms matter this time of year?

Early November is when heating systems, fireplaces and space heaters start running again after months of sitting idle, which is exactly when a fuel-burning appliance is most likely to develop a problem that produces carbon monoxide. It's a good moment to check every alarm in the house rather than wait for a colder week when a technician's schedule fills up.

If you're having a furnace or gas appliance serviced anyway, ask whoever comes out whether your CO alarms are placed where they should be.

What should you do if an alarm is missing, old or not working?

1. Count the alarms you have and compare against the placement guide above: one inside every bedroom, one outside each sleeping area, one on every level.
2. Check the manufacture date on the back of each smoke alarm. If you can't find a date, or it's been more than 10 years, replace the unit.
3. Test every alarm, smoke and CO, right now. Replace batteries in anything that doesn't sound.
4. Add any alarms you're missing. Plug-in and battery units are straightforward; a hardwired or interconnected system is electrical work for a licensed electrician.

Get your home's alarms in order

If you need alarms installed — especially a hardwired or interconnected system — book smoke and carbon monoxide detector installation with an independent local Pro.

Last updated September 2026.