Act now
Emergency: get outside and call 911
A sounding CO alarm is treated as real. Get everyone and the pets outside to fresh air, call 911 from outside, and stay out until responders say it is safe.
Why this happens
NFPA says to go outside right away, call 911 once outside, and stay out until emergency personnel say it is safe to go back in. Kidde says never to assume an alarm is going off by mistake, and EPA notes that because CO is invisible and odorless, it is harder to tell whether a CO alarm is false or a real emergency. CO comes from burning any fuel, not only gas. CDC lists cars and trucks, small engines, stoves, lanterns, grills, fireplaces, gas ranges and furnaces, and NFPA adds vehicles idling in a garage and water heaters or dryers that are malfunctioning or poorly vented, so having no gas appliances does not rule it out. Kidde says that any time a digital alarm shows a number, with or without an alert, you should assume it senses CO, leave the home and call 911.
Do this now
- Get everyone out now, pets included, to fresh air outdoors. Do not stop to look for the cause.
- Call 911 or the fire department from outside.
- Count heads once you are out. Stay outside and do not go back in for anything.
- Do not go back in to silence or reset the alarm, open windows, or switch anything off. Wait until responders say it is safe.
- If anyone feels unwell, tell the 911 operator and the responders. EPA says to go to an emergency room and say you suspect CO poisoning.
- If you cannot tell whether it was the CO alarm or the smoke alarm, treat it the same way: get out and call 911.
When to stop. Do not go back inside, even if the alarm has stopped, until responders say it is safe.
What to tell the HVAC technician
- Which alarm sounded, the sound it made, and whether its display showed a number.
- Who felt unwell, and whether anyone was asleep.
- Which fuel-burning things the home has: furnace, water heater, gas range, dryer, fireplace, space heater, generator or grill.
- Whether a car, generator or grill was running in or near an attached garage or close to a door or window.
Build the full list: what to tell the HVAC technician.
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