Generator carbon monoxide safety: where to put it and what to avoid

Updated 2026-10-31 · Sources linked inline

Run a portable generator outside only, more than 20 feet from any window, door or vent, with the exhaust pointed away from the house. Never run one in a garage, basement, crawlspace, shed or on a porch, even with the door open. That is the CDC's and the Consumer Product Safety Commission's guidance, and it exists because generators kill people every storm season.

How this guide was made: this is a research guide built on manufacturer specifications and federal guidance, with sources linked throughout. We haven't bench-tested any of the equipment mentioned, and we don't claim to.

How serious is it?

Carbon monoxide (CO) is an odorless, colorless gas. The CDC says it "kills without warning" and that each year more than 400 Americans die from unintentional CO poisoning not linked to fires, more than 100,000 visit an emergency department and more than 14,000 are hospitalized (CDC). Portable generators are named among the sources.

CPSC's own numbers are for generators specifically. In a briefing package covering 2010 to 2020, CPSC reported an average of 64 deaths per year when only a generator was involved, and 68 per year when a generator and another CO-producing product were involved. Three-quarters were single-fatality incidents, and one quarter involved multiple deaths, some of them entire families. Fatal incidents commonly involved a generator in the living space, attached garage, basement or crawlspace (CPSC briefing package).

The pattern is consistent: people run a generator "just for a few hours," "just inside the garage" or "with the door cracked," and the CO accumulates faster than ventilation can clear it. The danger is highest while people are asleep.

The placement rules

From the CDC and CPSC:

1. Outdoors only. Not inside the home, garage, basement, crawlspace, shed or on a porch. CPSC states that opening doors or windows won't provide enough ventilation to prevent lethal CO levels (CPSC), and says not to run one on a porch or in a carport because that is too close to the home.
2. More than 20 feet from the house. The CDC says more than 20 feet from windows, doors and vents. CPSC says at least 20 feet from the house. Farther is better, and the distance has to be measured to every opening, including a neighbor's.
3. Aim the exhaust away. Point the exhaust away from the home and from any other building someone could enter. Keep windows and openings closed in the exhaust path.
4. Mind the wind. If the wind pushes exhaust toward a window or door, move the generator or aim it differently. This is common sense, not a number from the sources.
5. Keep it dry, but not enclosed. CPSC warns of shock and electrocution in wet conditions. If you must run a generator in rain, use an open, canopy-like structure on a dry surface where water can't reach or puddle under it, without enclosing it or placing it near openings. Dry your hands before touching it.

Cords, not wiring

• Connect appliances using heavy-duty extension cords made for outdoor use, with a wattage rating above the total of everything connected to that cord. Check the whole length for cuts, and make sure the plug has all three prongs.
• Use cords long enough to let you place the generator outdoors and far from openings. If a cord passes through a window or door, protect it from pinching.
• Never backfeed. Don't plug a generator into a wall outlet to power house wiring. CPSC says it is extremely dangerous, can electrocute utility workers and neighbors, and bypasses household circuit protection (CPSC safety alert). To power house circuits, have an electrician install a transfer switch or interlock.

CO shutoff: what the standards actually say

Two voluntary standards from 2018 are meant to reduce CO deaths: UL 2201 and ANSI/PGMA G300. According to CPSC's briefing package, UL 2201 sets a maximum weighted CO emission rate of 150 grams per hour and requires the generator to shut off when CO measured one foot above the top centerline of the generator averages 150 ppm over 10 minutes, or reaches an instantaneous 400 ppm. CPSC's analysis estimated that generators meeting the G300-2018 standard would avert nearly 87 percent of CO deaths and generators meeting UL 2201 nearly 100 percent (CPSC briefing package). Those are modeled estimates, not guarantees. Newer 2023 editions of both standards now exist, and CPSC suggests looking for models certified to the latest versions (CPSC).

How to use that:

• Look for automatic CO shutoff on any generator you buy. Some models are advertised as certified to these standards. For example, Honda's EU2200i Companion lists a CO-MINDER system that automatically shuts the generator down before CO near the unit becomes dangerously high (Honda). That is one example, not an endorsement of a brand.
• Don't treat shutoff as permission to move the generator closer. The sensor protects the area around the generator; it doesn't monitor your living room.
• Check an older generator. A generator made before the 2018 standards likely lacks CO shutoff. Check the manual or label, and treat the placement rules as absolute.

CO detectors are not optional

The CDC's advice for portable generators is to use a battery-powered or battery backup CO detector in your home. It also says to:

• Install detectors near every sleeping area. Ready.gov and CPSC add that detectors should be on every level of the home (Ready.gov, CPSC).
• Check batteries when you change clocks in spring and fall.
• Replace detectors per the manufacturer's instructions or every 5 years.
• Consider a model with a digital readout that shows the highest CO concentration.

Most outages start with the grid down, so a plug-in-only detector may be useless. Choose one with battery power or battery backup.

Symptoms, and what to do

CO symptoms are often described as "flu-like": headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. If you breathe in a lot, you can pass out or die. People who are sleeping or impaired can die before symptoms show.

If a detector alarms or anyone has these symptoms near a running generator: get everyone out into fresh air immediately, call 911, and don't go back inside until emergency responders say it is safe. Turn the generator off only if you can do so without re-entering a contaminated space. In the U.S., Poison Help (1-800-222-1222) can also advise.

Other CO sources during an outage

The generator isn't the only risk when the lights go out. The CDC and Alabama Power both warn against:

• Using a gas oven or stove to heat the house.
• Burning charcoal indoors; charcoal grills, camp stoves and lanterns belong outdoors only.
• Using propane or gas heaters designed for outdoor use inside a home.
• Running a vehicle in an attached garage, even with the door open.

The Alabama Power winter guidance lists the same rule set: do not use a stove for heat, and do not use outdoor grills, gas/propane heaters or generators indoors (Alabama Power).

Neighbors and shared walls

Your detector can only protect you from your own generator. Check where neighbors set up theirs. If one is running close to your windows, ask them to move it. If you live in a duplex, townhome or apartment, don't use a generator on a balcony or patio near other units. This part is our advice, not a rule from the sources.

Quick pre-storm routine

For more on picking a unit, see generator vs power station (a battery power station has no exhaust, so no CO from the unit). For the full outage plan, use the Alabama outage checklist and the winter storm checklist. If you are heating with a gas furnace on generator power, read will a generator run a gas furnace.