Last verified: October 1, 2026
Run a portable generator outdoors only, more than 20 feet from your home, with the exhaust pointed away from windows, doors and vents, and have battery-operated carbon monoxide alarms working inside. Never run one in a garage, basement, crawl space, shed or porch, even with the doors open. These are the rules from the CDC and the Consumer Product Safety Commission, and they exist because generators are the leading consumer product behind carbon monoxide deaths.
Why generators are so dangerous
Carbon monoxide (CO) is invisible and has no smell. A gasoline generator produces a lot of it. The numbers are sobering:
- More than 400 Americans die each year from unintentional, non-fire CO poisoning, and there are more than 100,000 emergency department visits (CDC).
- Portable generators were linked to more than 85% of non-fire CO deaths associated with engine-driven tools in CPSC’s long-term data, and half of those deaths happened between November and February, when outages and cold weather drive people to run generators close to the house (CPSC).
The distances that matter
| Generator type | Rule | Source |
|---|---|---|
| Portable | Outdoors only, more than 20 feet from windows, doors and vents | CDC, CPSC |
| Portable | Never in a garage, basement, crawl space or enclosed porch, even with doors open | CDC |
| Standby (permanently installed) | Typically 5 feet from windows, doors and vents, per the manufacturer and NFPA 37, or more if local code requires | Generac |
Standby generators are designed and inspected for their position, and their exhaust is directed away from the house, so their required distances are shorter. Still, Generac itself warns that exhaust can enter through openings smaller than windows, such as cracks and HVAC intakes.
Carbon monoxide alarms
- Install CO alarms on every level of the home and near sleeping areas.
- Choose alarms with battery backup: during an outage, plug-in alarms without batteries don’t work.
- Test them monthly and replace batteries as the manufacturer recommends. The CDC suggests replacing alarms about every 5 years.
- Consider an alarm in any room next to where a generator runs, such as a room beside the garage.
Symptoms of CO poisoning
Headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion, often described as flu-like (CDC). People who are asleep can die before they notice anything.
If a CO alarm sounds or anyone feels these symptoms: get everyone outside into fresh air immediately and call 911. Don’t go back in until emergency responders say it is safe.
Practical setup for a portable generator
- Choose the spot before the storm: level ground, more than 20 feet from the house, downwind if possible, not under windows.
- Buy a heavy-duty generator cord long enough to reach your inlet box from that distance.
- Use a generator tent or canopy designed for running units if you need rain protection; never an enclosed shed.
- Look for portable models with automatic CO shut-off, which turn the engine off if CO builds up around the generator.
- Refuel only when the engine is off and cool.
Other generator hazards
- Backfeeding: never plug a generator into a household outlet. Use a transfer switch or interlock kit. See Interlock Kit vs Transfer Switch.
- Fuel storage: store gasoline in approved containers, away from living spaces and heat sources.
- Electrocution: keep the generator dry and use outdoor-rated cords.
Choosing and placing CO alarms
| Where | Why |
|---|---|
| Every level of the home, including the basement | CO spreads through the house; a single alarm can miss it |
| Outside each sleeping area | People who are asleep can’t notice symptoms |
| Near rooms attached to a garage | Garages are a common source of CO entry |
| On the side of the house facing the generator | Exhaust can enter through small gaps on that side |
Choose alarms that run on batteries or have battery backup; plug-in-only alarms stop working in exactly the situation where you need them. Test them monthly, follow the manufacturer’s replacement date, and replace batteries when prompted. The CDC suggests replacing CO detectors every 5 years or as the manufacturer instructs.
Real-world mistakes that cause poisonings
- Running a portable generator in the garage “with the door open”. CO builds up quickly and seeps into the house.
- Placing it under a window or next to a door to keep the cord short.
- Moving it onto a covered porch or under a carport to keep it out of the rain.
- Running it in a shed, even with the door open.
- Using a generator overnight without working CO alarms in the house.
Each of these is a version of the same problem: the generator is too close to, or partly inside, an enclosed space. The fix is always the same: outdoors, more than 20 feet away, exhaust pointing away from the house.
A safety checklist to print
- Generator outdoors, more than 20 feet from windows, doors and vents.
- Exhaust pointing away from the house and from neighbors’ windows.
- Battery-powered CO alarms tested and working on every level.
- Generator connected through an interlock or transfer switch, never through a wall outlet.
- Fuel stored in approved containers away from the house; refuel only with the engine off and cool.
- Everyone in the house knows the symptoms of CO poisoning and to get outside and call 911 if an alarm sounds.
Frequently asked questions
Is a standby generator safer than a portable?
Standby generators are installed outdoors in a fixed position, with clearances checked by the installer and inspector, and their exhaust is designed for that location. That removes the most common causes of portable generator poisonings. Even so, Generac warns that exhaust can enter through small openings, so CO alarms are still essential.
Do generators with CO shut-off make alarms unnecessary?
No. Automatic CO shut-off on a portable generator stops the engine if CO builds up around the generator itself. It doesn’t protect against exhaust drifting into the house from a generator placed too close. Keep alarms inside regardless.