Generator CO Poisoning Risks and Safe Placement Distances

Why Generator CO Is Deadly

Carbon monoxide (CO) is an odorless, colorless gas that forms whenever fuel burns. A portable generator's engine produces it in high concentrations, and the CPSC warns that one generator can emit as much CO as hundreds of cars. In an enclosed space such as a garage, basement, or shed, the gas can build up quickly and incapacitate or kill a person within minutes. More than 200 people in the United States die each year from accidental, non-fire CO poisoning linked to consumer products, and more than 100 of those deaths involve portable generators.

The CDC reports 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. Portable generators are a leading cause of these incidents because they are often placed in or near living spaces during power outages.

The 20-Foot Clearance Rule

The single most important rule for portable generator placement is distance. Both the CPSC and the CDC instruct users to operate a generator outdoors at least 20 feet from any window, door, or vent, with the exhaust pointed away from the home. This is the minimum distance; placing the generator farther away lowers the chance that exhaust will drift back inside.

The 20-foot measurement applies to every opening that can draw air into the house, including windows, doors, vents, and crawl space openings. A generator sitting on a porch or under an overhang can still push CO toward an open window or an air intake, so keep the machine clear of all openings and treat the house itself as the boundary. For a full checklist, see our generator safety checklist for outdoor use.

• Place the generator outdoors on a dry, level surface.
• Keep at least 20 feet from windows, doors, vents, and air intakes.
• Point the exhaust away from the home and any occupied building.
• Do not run the generator on a porch, in a carport, or under an open window.

Never Indoors or in a Partially Enclosed Space

A common and deadly mistake is running a generator in a garage with the door open, in a basement, or in a shed. The CPSC explicitly warns against operating a generator inside a home, garage, basement, crawlspace, or shed, even if doors and windows are open. CO can accumulate in these spaces and linger for hours after the engine stops.

Partial enclosure does not provide enough airflow. The EPA notes that CO levels can build up quickly in garages, sheds, and similar areas and can remain dangerous well after the unit is turned off. If you need backup power during an outage, place the generator outside and use extension cords to bring power into the home. This is also the right approach for anyone considering a portable generator rather than a permanently installed unit.

CO Alarms and Detectors

A working CO alarm is essential protection. The CPSC recommends installing battery-operated CO alarms, or alarms with battery backup, on every level of the home and outside sleeping areas. Interconnected alarms are best, because when one sounds they all sound. The CDC adds that you should check the batteries when you change your clocks in spring and fall and replace the detector according to the manufacturer's instructions or every 5 years.

The EPA suggests considering a detector with a digital readout, which can show the highest CO concentration in the home in addition to sounding an alarm. Whatever unit you choose, place it outside sleeping areas so that an alarm in the night is more likely to wake you.

How CO Sensor Shutdown Systems Work

Some portable generators include a built-in carbon monoxide sensor that automatically shuts off the engine when CO levels in the surrounding air become dangerous. These systems are designed to detect elevated CO concentrations and stop the generator before the gas reaches a level that could cause symptoms. The Federal Register's proposed safety standard for portable generators discusses CO shutoff requirements and references voluntary standards like UL 2201 and PGMA G300, which include both emission limits and automatic shutoff thresholds.

A CO sensor shutdown is a valuable backup, but it does not replace proper placement. The sensor only measures CO near the generator, and wind or air currents can carry exhaust away from the unit while still pushing it toward the home. Always follow the 20-foot rule and use outdoor placement as the primary defense. For more about these systems, read our explanation of CO sensors on generators and see generators with CO sensors.

Placement and Wind Direction

Wind direction matters even when you exceed 20 feet. Exhaust can drift through an open window on the far side of the house if the breeze is strong enough. Position the generator so that the exhaust outlet points downwind, away from the home, and keep it at a distance that accounts for outdoor air movement. The CPSC and CDC both emphasize that exhaust should face away from windows and doors, not just be a certain number of feet away.

If you use a generator for a recreational vehicle, place it at least 20 feet from the RV's openings, and never run it under the RV or in a camper shell. The same principles apply to tents and campers. For more about sizing a generator for RV use, see RV-ready generators or RV-ready inverter generators.

Symptoms and Emergency Action

Recognizing CO poisoning early can save lives. The CDC lists headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion as common symptoms. These often feel like the flu, but they clear up when you leave the area. At higher concentrations, CO causes impaired vision, reduced coordination, and can be fatal. People who are sleeping or under the influence of alcohol can die before they notice anything wrong.

If you suspect CO poisoning, get outside to fresh air immediately, then call 911. Do not re-enter the building until emergency responders arrive. Also, if you believe a generator caused a poisoning incident, you can report it to the CPSC through their website. Always let the CO alarm dictate your action, even if you do not feel symptoms.

For a complete outdoor safety checklist, see our generator safety checklist and what is a CO sensor on a generator.

What to pick for your use

Questions

How far should a generator be from a house?

Place the generator at least 20 feet from windows, doors, and vents, with the exhaust pointing away from the home. More distance is always safer.

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

No. The CPSC warns never to run a generator in a garage, basement, or shed, even with doors and windows open. CO can build up quickly and linger.

Do CO sensor shutdown systems make placement less important?

No. A CO sensor that shuts down the engine is a backup, not a replacement for correct placement. Wind can carry exhaust away from the sensor while still moving it toward the home.

How often should I replace a CO detector?

The CDC recommends replacing your CO detector according to the manufacturer's instructions or every 5 years. Check the batteries twice a year, for example when you change clocks.

What are the symptoms of CO poisoning?

Headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. Symptoms often feel like the flu but improve when you leave the area.