Carbon Monoxide From a Furnace: What to Do and How to Prevent It

If a CO alarm sounds or anyone has symptoms: leave the house and call 911 from outside. Don't look for the source. Don't go back in until responders say it's safe, and don't run the furnace again until it's been serviced. (CPSC, Carbon Monoxide Fact Sheet.) If you smell gas, leave the house and call Southwest Gas or 911 from outside.

Symptoms

The CDC lists headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion as common CO symptoms, often described as flu-like. If several people or pets feel sick at once, or symptoms ease when you leave home, take it seriously. Tell your doctor you suspect CO. (CDC, Carbon Monoxide Poisoning Basics.)

How a furnace can produce or leak CO

A gas furnace burns natural gas and vents the combustion gases outdoors. CO becomes a problem when combustion goes wrong or exhaust doesn't leave the house:

• Cracked or damaged heat exchanger. The heat exchanger separates combustion gases from the air you breathe. A crack can let exhaust mix into the airflow.
• Venting problems. CPSC says inspectors should check flues for blockages, corrosion, and partial or complete disconnections. Nests, debris, a disconnected vent pipe in the attic or closet, or a vent damaged during roof work can all keep exhaust inside.
• Poor combustion. Dirty burners or not enough combustion air can make a furnace produce more CO.
• Not a furnace, but common: CPSC warns never to run a car in an attached garage or use a gas oven to heat the home. Many Las Vegas furnaces sit in garages, attics or hall closets, so a CO alarm near the furnace isn't always the furnace's fault.

Prevention

• Yearly inspection. CPSC and CDC both recommend having the heating system professionally inspected and serviced every year, including chimneys and flues. See furnace tune-up.
• CO alarms. CPSC recommends UL 2034 CO alarms on every level of the home and outside sleeping areas, interconnected if possible, tested monthly, batteries replaced yearly. Replace alarms per the maker's instructions.
• Keep vents clear after roof work or storms.

When to call

After responders clear the house, or if you want the furnace and venting inspected, call (702) 738-6976 to schedule. Don't use a furnace that was identified as the CO source until it's been serviced (CPSC).

FAQ

What should I do if my CO alarm goes off?

Leave the house and call 911 from outside. Don't re-enter until responders say it's safe. (CPSC)

Can a furnace cause carbon monoxide?

Yes. A cracked heat exchanger, blocked or disconnected venting, or poor combustion can let CO into the home.

What are the symptoms of CO poisoning?

Headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion, per the CDC.

How often should a furnace be inspected for CO safety?

Every year, per CPSC and CDC.

Where should CO alarms go?

On every level of the home and outside sleeping areas, per CPSC.