Where Should CO Detectors Go in a Home With a Gas Furnace?

Quick answer: Put a carbon monoxide alarm on every level of the home and in a central spot outside each sleeping area, as CPSC and NFPA recommend. With a gas furnace, also cover the living space nearest the furnace and any rooms next to or above an attached garage. Follow the alarm maker’s instructions for mounting height and distance from appliances.

Where does the first CO alarm need to go?

Outside the bedrooms. Carbon monoxide is most dangerous when people are asleep and can’t notice symptoms, so the hallway just outside the sleeping area comes first.

Many Central Texas homes have split floor plans, with the primary bedroom on one side of the house and the other bedrooms on the other. Each sleeping area needs its own alarm. Two-story homes need at least one on every level. NFPA recommends interconnected alarms, so when one sounds, they all do.

Where should a CO alarm go if the gas furnace is in the attic?

In the living space below it. Most CO alarms aren’t rated for attic temperatures, and an Austin attic in August can pass 130°F, so an alarm up there may not work as designed. Put one in the hallway or room closest to where the furnace sits overhead, in addition to your bedroom-area alarms.

What about a furnace in a closet or the garage?

For a hall-closet furnace, place an alarm in the nearby hallway or room, at the distance the manual specifies. Many makers ask for several feet of space from fuel-burning appliances to avoid nuisance alarms from normal startup puffs.

For a furnace or gas water heater in the garage, cover the rooms that share a wall or ceiling with the garage. Car exhaust makes a garage a poor spot for the alarm itself, and garage temperatures swing outside many alarms’ rated range.

What height should a carbon monoxide alarm be mounted at?

Whatever the manufacturer says. CO mixes with room air, so wall, ceiling and plug-in models can all work when installed per their instructions. The manual is the tiebreaker.

Where should you not put a CO alarm?

• Right next to the furnace, water heater or range.
• In bathrooms, where steam can cause false alarms or damage the sensor.
• In attics, garages or other spaces outside the alarm’s temperature range.
• Next to supply vents, ceiling fans or open windows, where fresh air can dilute a reading.
• Behind curtains or furniture.

How do you keep CO alarms working?

Test them monthly with the test button, replace batteries as needed, and replace the whole alarm on the maker’s schedule. The replacement date is usually printed on the back. A yearly gas furnace inspection is the other half of the job: a technician checks the burners, venting and heat exchanger. See what a tune-up includes.

What should you do if the CO alarm goes off?

Get everyone outside to fresh air right away and call 911 from outside. Don’t go looking for the source and don’t go back in until responders say it’s safe. CPSC lists headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion as symptoms of CO poisoning. Heater smells like burning? covers other furnace warning signs.

Related guides: Hidden Home Hazards: Radon, CO, Asbestos, Lead Paint and Fire, Heater Smells Like Burning? What’s Normal and When to Call and What’s Included in an HVAC Tune-Up?.

About Gold Eagle Services: This guide comes from the team at Gold Eagle Services, a family-run Austin HVAC, indoor air quality and mold remediation company founded in 2017. We’re licensed (TACLA119235 and RCO1783), insured and bonded, and we serve homes across the greater Austin area.

Need help with this in your home? Learn about our heater repair and tune-ups, or call 512-489-4653 to schedule a visit.