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Generator Carbon Monoxide Safety Guide

Last updated:

Fact-checked by Marcus Hayes, Master Electrician (License #CA-EL-89241), 15 years generator installation experience.

Carbon Monoxide Kills

Portable generators produce carbon monoxide (CO) — an odorless, colorless, and lethal gas. CO from generators kills an estimated 70 to 80 Americans every year. Never operate a generator indoors, in a garage, or closer than 20 feet from any door, window, or vent. Always use a battery-powered CO alarm inside your home.

Key Takeaways

  • Place every portable generator at least 20 feet from any door, window, or vent, with the exhaust pointed away from the building.
  • Carbon monoxide from generators kills 70 to 80 people per year in the US — most during power outages when generators are used indoors.
  • Choose a generator with a built-in CO shutoff sensor. If yours lacks one, use a battery-powered CO alarm inside your home.
  • Never run a generator in a garage, basement, or shed — even with doors and windows open.
  • Early symptoms of CO poisoning mimic the flu: headache, dizziness, nausea, and confusion. If you suspect CO, get to fresh air and call 911.

How far should a generator be from the house?

A portable generator must be placed at least 20 feet from any door, window, or vent to prevent carbon monoxide from entering the home. The exhaust outlet must point away from the building. This 20-foot minimum applies to all gas and propane portable generators regardless of wattage — a small 2,200W inverter produces the same lethal CO as a 12,000W open-frame model.

The 20-foot rule is not a suggestion — it is the minimum safe distance established by the Consumer Product Safety Commission (CPSC) and confirmed by every major generator manufacturer, including Generac, Honda, and Westinghouse. At 20 feet with the exhaust pointed away, CO concentrations at the home's openings drop to safe levels. At 10 feet or less, CO can still enter through doors and windows even when they are closed.

What is a CO shutoff sensor?

A CO shutoff sensor (also called CO-MINDER, COsense, or CO Shield depending on the brand) is a built-in carbon monoxide detector that automatically shuts off the generator when CO levels near the unit reach a dangerous threshold. It is the single most important safety feature on a portable generator. If your generator does not have one, use a battery-powered CO alarm inside your home.

Different brands use different names for the same technology: Honda calls it CO-MINDER, Generac calls it COsense, Champion calls it CO Shield, and Westinghouse calls it CO Shutoff. All of them monitor CO levels near the generator and shut the engine off if dangerous concentrations are detected. This prevents CO from reaching lethal levels if the generator is accidentally placed too close to a structure or if wind shifts exhaust toward the home.

Not all generators have this feature. As of 2026, many budget models and older units still lack CO sensors. We mark every generator on this site that does not include a CO shutoff sensor with a prominent safety warning in our reviews and roundup pages.

Signs of carbon monoxide poisoning

Early symptoms of carbon monoxide poisoning include headache, dizziness, nausea, weakness, and confusion — often described as flu-like symptoms without a fever. As exposure increases, symptoms progress to vomiting, loss of consciousness, and death. If you or anyone near a generator experiences these symptoms, get to fresh air immediately and call 911.
CO Level (ppm) Exposure Time Symptoms
35 – 100 1 – 2 hours Headache, mild nausea
100 – 200 2 – 3 hours Headache, dizziness, nausea, fatigue
400 – 800 45 minutes Confusion, vomiting, loss of consciousness
800+ Under 1 hour Unconsciousness, death

Generator safety checklist

  1. 1. Place the generator at least 20 feet from any door, window, or vent, with exhaust pointing away from the building.
  2. 2. Never operate the generator indoors, in a garage, basement, shed, or crawlspace — even with doors open.
  3. 3. Install battery-powered CO alarms on every floor of your home and near sleeping areas. Test them monthly.
  4. 4. Use a heavy-duty outdoor-rated extension cord (12-gauge or thicker) rated for the generator's amperage.
  5. 5. Never refuel a running or hot generator. Let it cool for at least 2 minutes before adding fuel.
  6. 6. Keep the generator dry. If operating in wet weather, use a purpose-built generator tent — never a tarp that blocks airflow.
  7. 7. Never plug a generator directly into a wall outlet (backfeeding). This is illegal and kills utility workers.

Frequently Asked Questions

How far should a generator be from the house?
A generator must be placed at least 20 feet from any door, window, or vent to prevent carbon monoxide from entering the home. The exhaust must point away from the building. This 20-foot rule applies to all portable gas and propane generators, regardless of size.
Can I run a generator in my garage with the door open?
No. Never run a generator in a garage, even with the door fully open. Carbon monoxide can accumulate to lethal levels in minutes, and the open door does not guarantee adequate ventilation. Generators must always be operated outdoors at least 20 feet from any structure.
What are the symptoms of carbon monoxide poisoning from a generator?
Early symptoms include headache, dizziness, nausea, weakness, and confusion — often described as flu-like without a fever. As exposure increases, symptoms progress to vomiting, loss of consciousness, and death. If you suspect CO poisoning, get to fresh air immediately and call 911.
Do all generators have CO shutoff sensors?
No. As of 2026, many budget and older models do not include CO shutoff sensors. We mark every generator on this site that lacks a CO sensor with a prominent safety warning. If your generator does not have a built-in sensor, use a battery-powered CO alarm inside your home.
Can I run a generator in the rain?
Running a generator in the rain is dangerous unless it is protected by a purpose-built generator tent or enclosure. Water can cause electrical shorts and shock hazards. If you must operate in wet weather, use a properly ventilated generator cover — never a tarp that blocks airflow or traps exhaust.
How many people die from generator CO poisoning each year?
Carbon monoxide from portable generators kills an estimated 70 to 80 people per year in the United States, according to CPSC data. Most deaths occur during power outages when generators are used indoors or too close to the home.