Keep a generator outside, more than 20 feet from every opening.
By Self Reliance Daily ·
Run a portable generator outdoors, more than 20 feet from every window, door and vent. Point the exhaust away from your home and every other occupied building. Never run it in a garage, basement, crawlspace, shed, carport or porch, even with doors open.
A working CO alarm and the right cord support safe placement. They never make indoor generator use safe.
Why distance matters
“Outside” is only the first part of the rule.
Carbon monoxide, usually shortened to CO, has no color or smell. A generator engine can produce a dangerous amount before anyone understands what is happening. The U.S. Consumer Product Safety Commission says one portable generator can produce as much CO as hundreds of cars, and more than 100 people in the United States die each year from portable-generator CO poisoning.
Moving the machine through the garage door does not finish the safety job. CO can enter through a nearby window, door, vent, air conditioner or attic opening. A CPSC staff review of reported fatalities from 2012 through 2022 found that some deaths happened even when the generator was outdoors because it was close enough for exhaust to enter an occupied space.
The safe plan uses several layers at once: enough outdoor distance, exhaust pointed away, clear ventilation around the generator, working CO alarms inside and a power connection that does not force the machine closer to the house.
Do not ask whether the generator is technically outside. Ask whether its exhaust can reach any opening or occupied building.
The safe setup
Use four placement checks before starting the engine.
The current CDC guidance says more than 20 feet from windows, doors and vents. CPSC commonly says at least 20 feet from homes and buildings. This guide uses the stricter wording: more than 20 feet from every opening.
Check 1
Outdoors only
Never run a portable generator in a home, garage, basement, crawlspace, shed, carport, porch or other enclosed or partly enclosed space. Opening doors and windows or adding fans does not make these places safe.
Check 2
More than 20 feet away
Measure from the generator to every window, exterior door and vent, not just to the nearest wall. Check basement windows, dryer vents, soffit vents, fresh-air intakes and openings on nearby buildings too.
Check 3
Exhaust pointed away
Turn the exhaust away from your home and other buildings that people can enter. Distance and exhaust direction work together. Neither replaces the other.
Check 4
Clear and dry
OSHA generator guidance calls for 3 to 4 feet of clear space on every side and above the unit. Keep it dry and follow the owner’s manual without moving it near a building opening.
Indoor warning layer
Use CO alarms on every level and outside sleeping areas.
A CO alarm warns about dangerous gas that people cannot see or smell. During an outage, the alarm must still have power. The latest CPSC storm guidance recommends battery-operated CO alarms or alarms with battery backup on every level of the home and outside sleeping areas.
Interconnected alarms are useful because all units sound when one detects danger. Test alarms monthly. Replace batteries and the alarm itself according to the manufacturer’s instructions and end-of-life signal. Follow local placement rules if they require additional alarms.
CPSC's alarm standards page says a standalone consumer CO alarm should meet the applicable UL 2034 standard. A combination smoke and CO alarm should meet both UL 2034 and UL 217. A digital display can be helpful for showing the highest recorded CO level, but the display does not change the response: leave when the alarm sounds.
An alarm is a backup warning layer. It does not give permission to run a generator indoors, under a porch or closer than the safe distance. A generator with a built-in CO shutoff also remains an outdoor-only machine.
If an alarm sounds
Leave first. Do not search for the source.
Get everyone outside to fresh air immediately and call 911 from outside. Do not stay inside to open windows, silence the alarm or check the generator. Do not re-enter until emergency responders say it is safe. The most common symptoms include headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. Heavy exposure can cause unconsciousness or death. People who are sleeping, intoxicated or otherwise impaired can die before noticing symptoms. Read the CDC’s CO symptom guidance and keep your household’s wider emergency information with your first aid and safety basics.
Safe power connections
The cord must let the generator stay at the safe distance.
The CDC power-outage guide recommends an extension cord longer than 20 feet. Use individual heavy-duty cords made for outdoor use. The wattage rating of each cord must exceed the combined wattage of everything connected to that cord.
Before every use, inspect the full cord for cuts, tears, crushed spots, loose parts and missing or bent prongs. Use a grounded three-prong plug. Protect the cord from being pinched or crushed where it passes through a door or window. A specific wire gauge cannot be chosen safely from article advice alone because the load, cord length, generator outlet and manufacturer instructions all matter.
Connect appliances as the generator manual directs. Never plug a generator into a household wall outlet. This is called backfeeding. It can bypass household protection, start a fire and send dangerous electricity onto utility lines where it can injure or kill workers and neighbors.
Never buy or use a male-to-male cord. CPSC says these cords have exposed prongs that can become energized and have no legitimate household use. If you want to power selected home circuits, have a qualified electrician install the correct transfer equipment under local electrical code and utility requirements.
Water, fuel and fire
Do not solve one hazard by creating another.
Rain may tempt people to move a generator into a garage or onto a porch. Refueling may feel urgent when the power is still out. Both shortcuts can turn a manageable outage into an emergency.
Keep the generator dry
Water creates shock and electrocution hazards. Keep the generator on a dry surface where water cannot reach, puddle or drain under it. Dry your hands before touching the equipment. Follow the manufacturer’s wet-weather instructions.
If rain protection is needed, it must remain open and well ventilated. Never move the running unit into a building, partly enclosed space, porch or area near an opening.
Stop and cool before refueling
Never refuel a running generator. Turn it off and let it cool. Fuel spilled onto hot engine parts can ignite. Refuel outdoors, away from ignition sources, and follow the fuel and shutdown steps in the owner’s manual.
Inspect for damage or loose fuel lines before starting. Do not operate damaged equipment.
Store fuel outside living areas
Do not store gasoline, propane, kerosene or diesel inside the home. Use the properly labeled safety container required for that fuel and keep it away from fuel-burning appliances and ignition sources.
Local fire codes may set storage limits and locations. Follow those rules rather than stockpiling more fuel than you can store safely.
Common mistakes
These shortcuts are still unsafe.
The garage setup shown on the left is unsafe. A running generator never belongs in a garage.
“The garage door is open.” An open door does not stop deadly CO from building up or entering the home.
“It is under the porch, so it is outside.” A porch, carport, shed, overhang near vents or other partly enclosed area can trap exhaust or direct it into the building.
“The alarm will warn us before anything bad happens.” A working alarm is essential, but it is a last warning layer. It cannot make bad placement safe.
“The generator has an automatic CO shutoff.” CPSC recommends this feature when buying a generator, but it does not replace the outdoor-only and distance rules.
“This short cord is fine for tonight.” A short cord encourages unsafe placement. A damaged, indoor-only or overloaded cord adds fire and shock hazards.
“I can power the house through an outlet.” Backfeeding can electrocute utility workers or neighbors and can start a fire. Use qualified installation and approved transfer equipment.
“I will top off the tank while it runs.” A hot engine can ignite spilled fuel. Shut down and let it cool first.
“CO smells like exhaust, so I will notice it.” CO itself is colorless and odorless. Do not use smell as a warning system.
Practical checklist
Prepare the setup before the outage.
Planning the location, alarms and cords in daylight is safer than making those decisions during a storm.
Before an outage
Choose, inspect and test
Choose a dry outdoor location more than 20 feet from every opening.
Confirm the exhaust can point away from all occupied buildings.
Read the manual and complete required maintenance.
Install CO alarms on every level and outside sleeping areas.
Test alarms monthly.
Prepare long, outdoor-rated cords for the actual loads.
Keep battery lights and spare batteries ready.
While operating
Recheck the whole path
Recheck distance from windows, doors and vents.
Point exhaust away from homes and other occupied buildings.
Keep 3 to 4 feet clear around and above the unit.
Keep the generator, cords and hands dry.
Use properly rated cords without backfeeding.
Shut down and cool before refueling.
Never ignore symptoms or an alarm.
If danger appears
Leave and call
Get everyone outside immediately.
Call 911 from outside.
Do not silence the alarm and stay indoors.
Do not return to find the source.
Wait until emergency responders say re-entry is safe.
Have exposed people evaluated as responders direct.
Safety supplies
Compare the safety category, not a brand promise.
These categories support the official guidance. Product features never replace the generator manual, local code or safe placement.
Affiliate disclosure: As an Amazon Associate, Self Reliance Daily earns from qualifying purchases. The two search links below are affiliate links. Prices, listings and safety claims can change. Check the current product page, certification, cord rating and manufacturer instructions before buying. The images are category illustrations, not exact product photos.
Indoor warning
Battery-powered CO alarms
Best for: keeping CO detection active when household power is off.
Use flashlights, headlamps, lanterns or battery-operated candles instead of open flames. Keep compatible spare batteries with the lights. The CDC includes emergency lighting and extra batteries in its power-source checklist, and CPSC recommends battery lighting rather than candles during an outage.
For a wider plan covering light, phone charging and alerts before larger backup power, use the power basics guide.
Official sources used for this guide
This article uses U.S. federal safety guidance. Local building, fire and electrical codes may add requirements.
Generator safety is one part of a calm outage plan. Cover indoor lighting and phone power, first aid information and small-space supplies before the next warning arrives.
