Carbon monoxide alarm going off

Use this when

A CO alarm is sounding, or several people feel flu-like at home with no clear cause.

Done when

Responders have cleared the house and a qualified technician has dealt with the source.

Who

You, then responders, then a qualified technician

Written for this manual, last checked against sources November 4, 2026. Who wrote it

E-2.1 Treat every alarm as real

Carbon monoxide can't be seen, smelled or heard, so feeling fine tells you nothing. The Consumer Product Safety Commission's instruction fits on one line: if you suspect poisoning, get outside to fresh air immediately, and then call 911. The order matters. Outside first, phone second.

An alarm that keeps sounding isn't a faulty alarm until responders say so.

E-2.2 The same drill with no alarm

Symptoms are reason enough to leave. CDC lists headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion, often described as flu-like. People who are asleep or intoxicated can die before they notice any symptoms, so wake everyone.

E-2.3 Before anyone goes back

Responders decide when the house is safe. Ask them what must stay off. Then have a qualified technician find and fix the source before you use that appliance again. Common sources, per EPA, include leaking chimneys and furnaces, back-drafting furnaces, water heaters, wood stoves, fireplaces, gas stoves, unvented heaters, generators and exhaust from an attached garage.

E-2.4 Keeping it from happening again

• Alarms. CPSC says every level and outside sleeping areas, and in 2026 it said to test them monthly. CDC says to replace them per the maker or every 5 years.
• Colorado law. As published in Colorado's statutes, homes with a fuel-fired appliance, fireplace or attached garage need a working alarm within fifteen feet of each sleeping room's entrance when offered for sale, or after certain permitted work, on or after July 1, 2009. Rentals have their own rules.
• Service. CDC says to have heating and water heating equipment serviced by a qualified technician and the chimney checked or cleaned every year.
• Snow. Clear snow from outside vents for fuel-burning appliances. Nests, snow or ice inside a vent pipe are a job for a qualified technician.
• Generators. Run them outside only, at least 20 feet from doors, windows and vents. Never in a garage or carport.
• Heat in an outage. Never heat with a gas range or oven.
• Vehicles. Never run one in an attached garage, even with the door up.