Can you run a generator in a garage with the door open?

The answer is no, every time

• Not with the door open. CPSC says never to use a portable generator inside homes, garages, basements, crawlspaces or sheds, "even if doors or windows are open." NFPA says: "Never use a generator in an attached garage, even with the door open."
• Not in a detached garage. CPSC's list includes sheds and "other enclosed areas." Honda's manual says never to run one in a garage or "any enclosed or partially enclosed space."
• Not on propane. Propane engines make carbon monoxide too. Champion's dual fuel manual gives the same garage warning for gas and propane: "DO NOT operate the generator inside any building, including garages."
• Not "just for a few minutes." CPSC says CO "can kill within minutes, often before victims recognize symptoms."

Why an open garage door doesn't make it safe

It feels like it should. A two-car door is a huge opening. But the question isn't whether the garage clears out. It's whether CO gets into your house, and it does.

The government tested it. CPSC worked with NIST, the federal measurement lab, on a test house with an attached garage. CPSC's 2023 proposed rule describes the results. Two generators with CO shut-off, run in the attached garage "with the bay door fully open," produced:

• Not enough CO in the garage to trigger the shut-off. The open door kept the air near the generator just clean enough.
• CO levels in the living space "that would have caused injuries to the home's occupants."

In one test the generator ran 329 minutes, until it ran out of fuel. The modeled blood CO levels of people inside peaked at 27% to 37%. CPSC says that's the range for "severe headache, nausea, vomiting, and cognitive impairment." That's with the door wide open and a CO shut-off on board.

OSHA says it plainly: "Open windows and doors may NOT prevent CO from building up when a generator is located in an enclosed space."

What the CPSC death data shows

CPSC studied every generator CO death it found from 2011 to 2021.

• 103 deaths, in 77 incidents, happened with the generator in an attached garage, enclosed carport or attached barn. That's 18% of the generator CO deaths at fixed homes.
• 64 deaths, in 51 incidents, happened even though someone had opened a window, a door, a garage door, or a mix of these.
• 17 more deaths, in 13 incidents, happened while people tried to vent the exhaust out with fans or through a door or window.
• 13 deaths across all engine-driven tools involved a CO alarm that sounded but was misunderstood or switched off, or that sounded inside the house while the person died in the attached garage.

Open doors and windows were not enough to save them.

"My garage is detached. Is that OK?"

No. It's still an enclosed building.

• CPSC's warnings cover garages, sheds and "other enclosed areas," whether attached or not.
• CPSC's report found 7% of generator CO deaths happened in detached structures at home, like detached garages and sheds.
• A detached garage is often close to the house, or to a neighbor's. Ready.gov and CPSC both say 20 feet from homes and buildings.
• You'd be inside it with the generator, refueling, checking it or plugging things in.

"What if I run it just outside the garage door?"

Only if it's at least 20 feet from the house, and from the attached garage, with the exhaust pointed away. Ready.gov says generators should be at least 20 feet "away from windows, doors and attached garages." Right in front of an open garage door is a common way CO gets into a home. See how far a generator should be from the house.

Why do people do it?

Usually for one of three reasons. Each has a safe answer.

The reason	The safe answer
Rain or snow	A canopy or a cover made for running generators, outdoors and 20+ feet away. See running a generator in the rain.
Theft	Chain it to something solid outdoors, 20+ feet from the house.
Noise or cord length	Buy a longer, heavier cord. Never shorten the distance.

Storing it in the garage is fine

Storing a cool, switched-off generator in a garage is different from running it there. Honda's storage advice is to pick a well-ventilated spot away from furnaces, water heaters, dryers and other flames, and Champion says to let it cool before you store it. Wheel it outside, at least 20 feet from the house, before you start it. See how to store a generator.

Signs of CO poisoning, and what to do

Common symptoms include headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion, CPSC says. It can feel like the flu.

If you feel any of these with a generator running, or a CO alarm sounds:

1. Get everyone out into fresh air right away.
2. Call 911 from outside.
3. Don't go back in to find the problem or shut the generator off.

Put battery or battery-backup CO alarms on every level of your home, as Ready.gov advises. Full details are in our generator carbon monoxide safety guide.

If you need power indoors

Only a battery power station is safe to run inside. It has no engine and no exhaust. See portable power station vs generator.

Run a generator outdoors only, 20+ feet from the house, away from windows and doors: generator carbon monoxide safety.