Choosing Smoke and CO Alarms

Know the two smoke sensor types

Smoke alarms use ionization sensors, which respond quickly to fast flaming fires, or photoelectric sensors, which respond better to slow smoldering fires. Many experts recommend dual-sensor alarms that cover both, so you are protected regardless of how a fire starts.

Do not forget carbon monoxide

Carbon monoxide is odorless and comes from fuel-burning appliances like furnaces, water heaters, and attached garages. If your home has any gas appliance or an attached garage, you need CO alarms. Combination smoke and CO units cover both in one device to keep placement simple.

Sealed ten-year versus replaceable battery

Sealed ten-year alarms have a non-removable battery that lasts the full life of the unit, so there is nothing to swap and no low-battery chirp at 3 a.m. Replaceable-battery units cost less up front but need fresh batteries yearly. For most homeowners the sealed units are worth the small extra cost.

Placement basics

• One alarm inside each bedroom
• One in the hallway outside sleeping areas
• At least one on every level, including the basement
• CO alarms near sleeping areas and fuel-burning appliances
• Replace any alarm older than ten years
• Test every alarm monthly

Alarms worth buying

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Common questions