Generator carbon monoxide safety: how far from the house, alarms and symptoms

A portable generator's exhaust contains carbon monoxide (CO). You can't see it or smell it. CPSC warns that it "can kill you in minutes," and that one generator produces as much CO as hundreds of cars. Every year people die after running a generator in a garage, basement or right next to the house during an outage.

These rules come from CPSC, NFPA, OSHA and CDC. Follow every one of them, every time.

Where should you put a generator?

Outdoors only. At least 20 feet from your home.

• 20 feet or more from your house and any building, CPSC says, with the exhaust pointed away from windows, doors and vents. NFPA says to measure the 20 feet from the generator to the building.
• Never inside a home, garage, basement, crawlspace or shed, CPSC says, "even if doors or windows are open."
• Never in an attached garage, even with the door open, NFPA says.
• Not on a porch, under a carport, or under a deck or overhang. Exhaust can collect there and drift inside.
• Keep 3 to 4 feet of clear space on all sides and above it, OSHA says.
• Not near a neighbor's windows either. Their home counts too.
• Don't stand or sit downwind of the exhaust. NFPA says: "If you can smell exhaust, you are inhaling it."

Fans and open windows do not make an indoor or garage generator safe. OSHA notes that open windows and doors may not stop CO from building up in an enclosed space.

CO alarms: every level of your home

• Put a CO alarm on every level of your home, Ready.gov advises.
• Follow the alarm maker's instructions for placement and mounting height, NFPA says.
• Test alarms monthly and replace batteries if needed, CPSC says.
• Use battery or battery-backup alarms. A plug-in-only alarm won't work in an outage.

If a CO alarm sounds, don't look for the problem. Get everyone outside to fresh air right away, then call 911.

Look for a CO shut-off generator

CPSC urges buyers to look for portable generators with a carbon monoxide shut-off feature. The generator senses rising CO around it and turns itself off.

CPSC also says models certified to the latest PGMA G300-2023 and UL 2201-2023 standards include CO safety technology. It adds that UL 2201 certified models also have reduced CO emissions, not just the shut-off.

A shut-off is a backup, not permission to bend the rules. One maker's product page says its CO shut-off "is not a substitute for an indoor carbon monoxide alarm or for safe operation." Keep the generator 20+ feet away and keep your alarms working.

Is a CO shut-off required by law? Not by a federal rule, as of October 2026. CPSC proposed a mandatory standard that would limit generator CO emissions and require shut-off. It published a supplemental proposal on April 20, 2023. We found no final rule in the Federal Register as of September 30, 2026. So it's a proposal, not the law.

Symptoms of carbon monoxide poisoning

CDC lists the most common symptoms:

• headache
• dizziness
• weakness
• upset stomach or vomiting
• chest pain
• confusion

CDC says CO symptoms are often described as "flu-like."

CO can make you pass out or kill you. CDC warns that people who are asleep, drunk or under the influence can die from CO before they have any symptoms. That's why the alarms matter so much at night.

What to do if you suspect CO poisoning

1. Get everyone into fresh air right away. Don't stop to open windows or find the source.
2. Call 911 from outside.
3. Get medical care, even if people start to feel better. OSHA says to seek medical attention.
4. Don't go back in until emergency crews say it's safe. OSHA says not to re-enter until trained, properly equipped people say it's safe.
5. Shut the generator off only if you can do it without going into the fumes.

Fire and refueling

Generators get hot, and stay hot after you shut them off.

• Turn the generator off and let it cool before refueling. NFPA says never refuel while it's hot. Ready.gov and OSHA both warn that fuel spilled on hot engine parts can ignite.
• Store fuel in an approved, labeled container, OSHA and NFPA say, outside living areas. Don't store gas in your home.
• Keep fuel away from flames and heat, including the generator itself, water heaters, cigarettes and lighters, OSHA says.
• Don't overload it. OSHA warns overloading can cause overheating and fire.
• Plug appliances straight into the generator, or use heavy-duty, outdoor-rated, three-prong cords, NFPA says. Check cords for cuts first.

Can you run a generator in the rain?

Not unprotected. OSHA says to keep a generator dry and not use it in rain or wet conditions, and to protect it with a canopy if needed. Generac says never to run a generator directly in rain, snow or other wet conditions. CPSC says to follow the maker's instructions for wet weather.

What that means in practice:

• Use a vented cover made for running generators, or an open canopy, out in the open, 20+ feet from the house.
• Never move the generator into a garage, shed, carport or onto a porch to keep it dry. That's how people get poisoned.
• Set it on a dry, level spot, out of puddles.
• Dry your hands before you touch it. OSHA says never handle a generator's electrical parts when you're wet or standing in water.
• Use GFCI protection in damp areas, OSHA advises.

Never connect a generator to your house wiring yourself

Never plug a generator into a wall outlet. Power can flow back onto the utility lines. OSHA warns this "can energize wiring systems for great distances," putting utility workers and neighbors at risk. If you want to power house circuits, have a licensed electrician install a transfer switch or listed interlock kit. See interlock kit vs transfer switch.

Your quick safety checklist

• Generator outdoors, 20+ feet away, exhaust pointed away from the house
• Not in a garage, basement, shed, carport or porch
• 3 to 4 feet of clear space all around
• CO alarms working on every level
• Refuel only when it's off and cool
• Fuel stored outside living areas in an approved can
• Cords outdoor-rated and undamaged
• No backfeeding, ever

If you'd rather not deal with fumes at all, a battery power station has no exhaust. See portable power station vs generator.