Portable generators are safe machines when they are used the way their manuals describe, and dangerous when they are not. According to the U.S. Consumer Product Safety Commission, an average of nearly 100 people die each year in the United States from carbon monoxide poisoning caused by portable generators, almost always because the generator was run indoors or too close to the house. The rules below are short, and they work.
Quick answer
Run the generator outdoors only, at least 20 feet from the house with the exhaust pointing away from doors, windows and vents. Never run it in a garage, basement, shed, carport or on a porch, even with doors open. Fit carbon monoxide alarms on every level of the home. Let the engine cool before refueling, use heavy outdoor-rated cords, and never plug it into a wall outlet.
In this guide
Carbon monoxide
Carbon monoxide (CO) is a colorless, odorless gas produced by every fuel-burning engine. A portable generator produces far more of it than a car. In an enclosed or partly enclosed space it can reach a deadly level within minutes, and because it causes drowsiness and confusion, people often do not realize what is happening.
- Outdoors only. Not in a garage with the door open, not under a deck, not in a carport, not in a doorway.
- At least 20 feet from the house, with the exhaust pointed away from windows, doors and vents, including your neighbors’.
- CO alarms on every level and outside sleeping areas. Choose battery-powered or battery-backup models so they work during the outage. Test them when you test the generator.
- Look for a CO shutoff. Newer generators can sense CO building up around them and stop the engine. The CPSC recommends models certified to the PGMA G300 or UL 2201 standards. Treat the sensor as a last line of defense, never as permission to run the generator closer.
Placement
- Set the generator on a level, dry surface where rain and snow will not reach the outlets. A generator tent or canopy designed for the purpose keeps it dry without trapping exhaust. Do not improvise an enclosure.
- Keep it clear of dry grass, leaves and anything that can burn. The muffler gets hot enough to start a fire.
- Secure it with a chain and lock if theft is a risk, but do not block the airflow.
- Keep children and pets away. Surfaces are hot and the outlets are live.
Fuel
- Shut the engine down and let it cool for several minutes before refueling. Gasoline spilled on a hot engine or muffler can ignite.
- Store fuel outside living areas, in approved containers, away from any water heater, furnace or other appliance with a pilot light or burner.
- Do not overfill the tank. Fuel expands as it warms.
- Keep a fire extinguisher rated for flammable liquids (class B) near the generator and fuel.
- Know your local limits. Fire codes restrict how much gasoline can be stored at a home. See how long gasoline lasts for storage advice.
Electrical safety
- Never backfeed. Do not plug a generator into a wall outlet. Use extension cords to appliances, or a transfer switch or interlock installed by an electrician. Our guide explains how to connect a generator to your house safely.
- Use heavy-duty, outdoor-rated cords in good condition, sized for the load, and never run them under rugs or through standing water.
- Keep the generator dry and operate it with dry hands. Water and electricity together cause electrocution.
- Do not exceed the rated output. Overloading trips breakers at best and overheats wiring at worst. Size the generator with headroom using our sizing guide.
- Ground the generator if the manual or local code requires it.
Before an outage
- Read the manual once, properly, while the lights are on.
- Test-run the generator under load every month or two so you know it works and remember how to use it.
- Keep the cords, funnel, oil and a flashlight with the generator.
- Plan where it will sit, measure the 20 feet, and make sure a cord of that length reaches.
Our power outage checklist covers the rest of the preparation.
Frequently asked questions
Can I run a generator in the rain?
Not uncovered. Water on the outlets or control panel risks electrocution and damage. Use a canopy or tent designed for generators, which keeps the rain off while leaving the engine open to the air, and set the generator on a dry, level surface.
How far should a generator be from the house?
At least 20 feet, with the exhaust pointing away from the building. That distance comes from the Consumer Product Safety Commission's guidance and applies to neighbors' homes as well as your own.
Is it safe to run a generator overnight?
It can be, provided it is outdoors at a safe distance, you have working CO alarms, and the fuel level and oil will last until morning. Never refuel a hot generator half-asleep in the dark, and do not run cords through a window you then cannot close.
Can carbon monoxide from a generator get into the house from outside?
Yes, if the generator is close to the house or the exhaust points at an opening. CO drifts in through windows, doors, vents and soffits. The 20-foot distance and exhaust direction exist for exactly this reason.
Further reading: the CPSC Carbon Monoxide Information Center and the Ready.gov power outage guidance.
