The covered porch is still inside for carbon monoxide
A covered porch counts as indoors for carbon monoxide. Learn the 20-foot rule, safe generator placement, and how to set up CO alarms.
01Power & Backup
The CO Alarm Went Off. Leave First, Then Call
When a carbon monoxide alarm sounds, a lot of people open a window and go back to bed. What to do instead, the symptoms to know, and why an old alarm needs replacing, not just a new battery.
- Read
- 2 min
- Updated
- October 5, 2026
A carbon monoxide alarm goes off at 2 a.m. during an outage. The most common reaction: open a window, push the button, go back to bed.
Don't. Here's what to do.
01When it sounds
- Get everyone out. People and pets. Into fresh air, outside.
- Call 911 from outside. Tell them the CO alarm went off. Fire departments have meters and will check the house.
- Call Poison Control at 1-800-222-1222 if anyone has symptoms or you're unsure what to do.
- Don't go back in until the fire department says it's clear.
Opening a window lowers the reading for a few minutes while the source keeps running. CO keeps building and you're asleep.
02Symptoms
Carbon monoxide symptoms feel like the flu: headache, dizziness, nausea, weakness, confusion, sleepiness. Two warning signs:
- More than one person in the house feels sick at the same time.
- People feel better when they leave the house.
Pets often get sick first.
03Common sources in an outage
- A generator too close to the house, or in the garage. See where the generator goes when it's raining.
- A car running in an attached garage
- Using the oven or a gas range to heat the house
- A charcoal grill or camp stove indoors
- A blocked furnace or water heater vent (snow, ice, leaves)
04Check your alarms now
- One on every level of the house and near bedrooms.
- Test them with the button.
- Check the date on the back. CO alarms wear out. Many need replacing after about 5 to 10 years, depending on the model, even if the battery is fresh. Many beep a special pattern at end of life.
- Battery backup on plug-in or hardwired alarms, so they work when the power is out.
05False alarm?
Maybe. But you can't tell from inside the house. Let the people with the meter decide.
See also generator safety and carbon monoxide and heating a home without power safely.
Sources (2)
Newswise / NJ Poison Control at Rutgers · Montgomery County Police Reporter: Conroe CO calls
Photo by Kanenori on Pixabay.
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