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Carbon Monoxide (CO) Alarm FAQs

What is a CO alarm?

     A CO alarm detects CO and produces a distinctive audible alert when CO is detected. It may be a stand-alone unit or part of an alarm system.

What types of CO alarms are available?

     CO alarm: Activated by CO; Smoke/CO alarm: Activated by smoke or CO; and Gas or Explosive Gas/CO alarm: Activated by CO, propane, or natural/methane gas. CO alarms must be battery-operated or receive their primary power source from the building wiring with a battery backup. Plug-in devices must have a battery backup. 

What is a CO source?

     A heater, fireplace, appliance (e.g., furnace, dryer, or water heater), or cooking source (e.g.., stove, oven) that uses coal, kerosene, petroleum products, wood, or other fuels (e.g., oil or natural gas) that emit CO as a by-product of combustion; or an attached garage with an opening that communicates directly with a living space.

Where do I install CO alarms?

     Install CO alarms on each level of your home with bedrooms (sleeping areas).

  • A CO alarm must be located within each bedroom or within 15 feet outside of each bedroom door. Bedrooms on separate floors in a structure containing two or more stories require separate CO alarms.
  • All CO alarms must be installed in accordance with the manufacturer's recommended instructions. (OAR 837-047-0130)


Are CO alarms required in bedrooms?

     No. A carbon monoxide alarm must be located within each bedroom or within 15 feet outside of each bedroom door. Ductwork from CO sources often goes directly to bedrooms, bypassing the hallways outside of them. For best protection, CO alarms are recommended in bedrooms and in the hallway.

May I replace a hard-wired smoke alarm with a combination CO /smoke alarm?

     Yes. You may replace a hardwired smoke alarm with a hardwired with battery back-up combination CO/smoke alarm.

  • Switching from one manufacturer’s unit to another may require a power adapter plug.
  • Manufacturers advise that adapter plugs may be changed using wire nuts and may require the services of a licensed electrician.

Are CO alarms required on every level?

     No. They are required on each level with bedrooms (sleeping areas).

How often do I replace my CO alarm?

     CO alarms should be replaced when the end-of-life signal is activated, the manufacturer’s replacement date is reached, or when they fail to respond to operability tests.

How do I keep my CO alarm working?

     Test alarms monthly. CO alarms must be maintained, tested, and batteries replaced according to the manufacturer’s recommended instructions. 

What should I do when the CO alarm sounds?

     Get outside to fresh air and call 911 or your local emergency number for help. If anyone is experiencing the symptoms of CO poisoning, get medical attention immediately.

Smoke and CO Alarm Safety Brochure (English/Spanish)
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