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Generator carbon monoxide safety: distance, garages and CO alarms

Run a portable generator outside only, at least 20 feet from the house, with the exhaust pointed away from buildings. Never run it in a garage, even with the door open. The CPSC says about 100 people die in the US each year from carbon monoxide from portable generators.

Published , by Alex Rowan

Review pending. This page hasn’t been checked by a qualified safety reviewer yet. Until it is, treat your owner’s manual and the sources at the end as the final word.

Why a generator indoors kills so fast

A gasoline engine’s exhaust contains carbon monoxide, a gas you can’t see or smell. The CPSC says a generator in a confined space can produce high levels of CO within minutes, and those levels can linger for hours after the generator shuts off. Not smelling exhaust doesn’t mean you’re safe. Most of the generator incidents reported to the CPSC involve CO poisoning from generators run indoors or in partly enclosed spaces.

Every portable generator made or imported since May 14, 2007 carries a CPSC-required danger label that says: “Using a generator indoors CAN KILL YOU IN MINUTES.”

Where to put the generator

Location Safe?
Inside the house, basement or crawlspace Never
Garage, including with the door open Never
Shed or other enclosed outbuilding Never
Porch or carport No. The CPSC says it’s too close to the home
Outside, 20 feet or more from the house, exhaust pointed away Yes

The CPSC and Ready.gov both use 20 feet. NFPA adds how to measure it: from the generator to the building, keeping at least 20 feet from all doors, windows and vent openings. Fans and open windows don’t make an indoor spot safe (CPSC).

Your neighbors’ windows count too. Point the exhaust away from any building, not only yours. Your owner’s manual may add its own placement rules for your model, and you should follow those as well.

Carbon monoxide alarms

A generator outside can still push CO into the house through a window or vent, so you need alarms inside.

  • Put battery-operated alarms, or plug-in alarms with battery backup, on every level of the home and outside sleeping areas. The CPSC says interconnected alarms, which all sound when one does, are best.
  • Buy alarms certified to UL 2034, IAS 6-96 or CSA 6.19.01 (CPSC).
  • Test them monthly and replace batteries as needed.
  • Follow the alarm maker’s instructions for placement and mounting height (NFPA).

Symptoms, and what to do

Honda’s EU2200i manual lists the early symptoms of CO exposure as headache, fatigue, shortness of breath, nausea and dizziness. Continued exposure leads to loss of coordination, loss of consciousness and death. The CDC adds that people who are sleeping, drunk or under the influence of other substances can die from CO poisoning before they have symptoms. That’s why the alarms matter.

  • If anyone feels sick, dizzy or weak while a generator is running, get to fresh air right away. The CPSC’s wording is “DO NOT DELAY.”
  • If a CO alarm sounds, get everyone outside immediately and call 911 (CPSC).

What a CO shut-off does, and doesn’t do

Some generators have a sensor that stops the engine when carbon monoxide builds up around it. The CPSC recommends looking for one. Two voluntary standards cover these features, PGMA G300-2018 and UL 2201. UL 2201 also requires the engine to emit less CO in the first place.

In a 2022 report, CPSC staff simulated 511 known deaths. They estimated that generators meeting PGMA G300-2018 would have prevented about 87% of them and generators meeting UL 2201 nearly all of them. These are modeled estimates. CPSC found that few generators on the market met UL 2201.

A shut-off is a backup. Honda’s manual for its CO-MINDER system says it “cannot prevent all danger” and tells owners to keep paying attention to where the generator sits. Treat the 20-foot rule as the protection and the sensor as the backup.

Other CO sources during an outage

  • Never use a gas stove or oven to heat the house (Ready.gov).
  • Never burn charcoal indoors or in a garage, even with the door open (CPSC).
  • After snow, clear the outside vents of fuel-burning appliances such as furnaces so exhaust can escape (CPSC).

A battery power station makes no exhaust, which is why many households use one for overnight power. The power station vs generator guide compares the two.