Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
A generator is the one piece of equipment most people buy, store, and then use for the first time in the dark, in bad weather, in a hurry. That is exactly when it kills someone. The exhaust carries carbon monoxide, which you cannot see or smell, and the CPSC's own wording is that it is deadly and can kill you in minutes, and that one generator produces as much carbon monoxide as hundreds of cars. Nothing on this page is about getting more power out of the machine. It is about where the machine stands.
The number people search for is the distance from the house, and there are three published answers to it, which is why this page exists. CPSC says to operate generators outdoors only, at least 20 feet from homes and buildings, with exhaust directed away from windows, doors and vents. CDC says only use generators outside, more than 20 feet away from any windows, doors, and vents — the same figure measured from a different thing. Honda, writing about its own machines, gives at least three feet from buildings, which is a cooling and fire clearance and is not a carbon monoxide setback at all. This page publishes all three, names who said which, and does not blend them into a house number, because the reason they differ is that they answer different questions.
Necessary equipment
| Item | Note |
|---|---|
| Tape measure | A tape measure gives you the distance from the building. |
| Carbon monoxide alarm | CPSC tells you to have a carbon monoxide alarm in the house. |
| Flashlight | You do this work in the dark. |
| Documentation for your generator | The manufacturer gives the position for its own machine. |
| Marker pegs optional | Pegs show the correct position again in bad weather. |
| Outdoor extension cord for the load material | The documentation for your generator gives the cord for your machine. |
Plan the position before the power stops
Estimated 24 min to 45 min
READ THE DOCUMENTATION FOR YOUR OWN GENERATOR FIRST.
The manufacturer can give a different distance for its machine.
- Read the safety section of the documentation for your generator.10mReport a problem with step 1, Plan the position before the power stops
- The manufacturer gives the position for its own machine.
- Honda gives at least three feet (one meter) from buildings for its generators.
- Honda gives that distance for cooling around the machine.
- A cooling distance is not a carbon monoxide distance.
- Walk around the building and find the possible positions in daylight.7mReport a problem with step 2, Plan the position before the power stops
- Find the windows, the doors and the vents on each wall.
- A dryer vent and an air intake are also openings.
- Look at the position of the neighbour buildings also.
KEEP THE GENERATOR DRY.
Water on the machine or on your hands can give you an electric shock.
- Select a position that is level and that stays dry.3mReport a problem with step 3, Plan the position before the power stops
- A level position keeps the engine oil at the correct height.
- Water on the machine can give you an electric shock.
KEEP THE GENERATOR AWAY FROM DRY GRASS, LEAVES AND OTHER MATERIALS.
The exhaust is very hot. These materials can catch fire.
- Remove the dry grass and the leaves from the position.4mReport a problem with step 4, Plan the position before the power stops
- The exhaust is very hot.
- Keep the position clear of stored materials.
Keep the generator outside
Estimated 11 min to 25 min
Source: Generators and Engine-Driven Tools · tier 1 · accessed 2026-07-29
OPERATE THE GENERATOR OUTSIDE ONLY.
DO NOT OPERATE IT IN A HOUSE, A GARAGE, A BASEMENT, A CRAWLSPACE OR A SHED. Carbon monoxide in the exhaust can kill you in minutes.
- Put the generator outside the building.3mReport a problem with step 1, Keep the generator outside
- CPSC tells you to use a portable generator outside and far from the home.
- CPSC names the home, the garage, the basement, the crawlspace and the shed.
- Honda gives the same instruction for its own generators.
DO NOT OPEN A DOOR OR A WINDOW TO MAKE AN ENCLOSED SPACE SAFE.
CPSC states that this does not give enough ventilation. Carbon monoxide collects and kills the people inside.
- Do not put the generator in a partially enclosed space.2mReport a problem with step 2, Keep the generator outside
- A garage with an open door is a partially enclosed space.
- A space below a deck or a canopy is also a partially enclosed space.
- CPSC states that open doors and windows do not give enough ventilation.
- Do not put the generator in a porch, a carport or a tent.1mReport a problem with step 3, Keep the generator outside
- CDC names the home, the garage and the carport.
- A cover above the machine holds the exhaust gas near it.
- Read the documentation for your generator about covers for wet weather.5mReport a problem with step 4, Keep the generator outside
- A tarpaulin or a box around the machine makes a partially enclosed space.
- The manufacturer names the covers that its own machine accepts.
Measure the distance from the building
Estimated 12 min to 25 min
Source: CPSC Warns of Generator, Carbon Monoxide and Fire Hazards Ahead of Hurricane Season · tier 1 · accessed 2026-07-29
Source: Carbon Monoxide Poisoning Basics · tier 1 · accessed 2026-07-29
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
PUT THE GENERATOR AT LEAST 20 FEET FROM EVERY BUILDING.
CPSC gives this distance. Carbon monoxide can enter a building and poison the people inside.
- Measure at least 20 feet from the building to the generator.5mReport a problem with step 1, Measure the distance from the building
- CPSC gives at least 20 feet from homes and buildings.
- CDC gives more than 20 feet from any window, door or vent.
- The two agencies do not measure from the same point.
- Obey both statements. Do not use a distance between them.
- Measure the distance to each window, door and vent also.4mReport a problem with step 2, Measure the distance from the building
- A wall with no opening is not the nearest point.
- A basement window at ground level is an opening.
- Measure the distance to the buildings of your neighbours.3mReport a problem with step 3, Measure the distance from the building
- Carbon monoxide from your generator can enter another home.
- Tell your neighbours before you start the engine.
Point the exhaust away from the building
Estimated 6 min to 11 min
Source: CPSC Warns of Generator, Carbon Monoxide and Fire Hazards Ahead of Hurricane Season · tier 1 · accessed 2026-07-29
POINT THE EXHAUST AWAY FROM THE BUILDING BEFORE YOU START THE ENGINE.
Exhaust gas that moves to a window can poison the people inside.
- Turn the generator until the exhaust points away from the building.2mReport a problem with step 1, Point the exhaust away from the building
- CPSC gives the exhaust directed away from windows, doors and vents.
- Honda gives the same instruction for its own generators.
- Find the exhaust outlet on your machine before you turn it.
DO NOT TOUCH THE EXHAUST OF THE GENERATOR.
The exhaust becomes very hot and can burn your hand.
- Look at the direction of the wind.1mReport a problem with step 2, Point the exhaust away from the building
- Wind can move the exhaust gas to the building.
- Turn the machine again if the wind changes.
- Close the windows and the doors that are near the generator.3mReport a problem with step 3, Point the exhaust away from the building
- CPSC tells you to close the windows near the generator.
- CPSC also tells you to seal the vent openings near the generator.
Install the carbon monoxide alarms
Estimated 16 min to 30 min
Source: Carbon Monoxide Poisoning Basics · tier 1 · accessed 2026-07-29
INSTALL A CARBON MONOXIDE ALARM IN THE BUILDING BEFORE YOU START THE ENGINE.
You cannot see or smell carbon monoxide. The alarm is your only warning.
- Install a carbon monoxide alarm on each level of the building.10mReport a problem with step 1, Install the carbon monoxide alarms
- CDC gives a battery-powered alarm or an alarm with a battery backup.
- A mains alarm with no battery stops when the power stops.
- Do a test of each alarm with its test button.3mReport a problem with step 2, Install the carbon monoxide alarms
- Do this test before each use of the generator.
- Replace the battery if the alarm does not sound.
- Tell each person in the building about the symptoms of carbon monoxide.3mReport a problem with step 3, Install the carbon monoxide alarms
- CDC names a headache, dizziness and weakness.
- CDC also names an upset stomach and vomiting.
- CDC also names chest pain and confusion.
- CDC states that these symptoms are frequently like influenza.
Start the generator
Estimated 12 min to 32 min
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
NEVER CONNECT THE GENERATOR TO THE WIRING OF A BUILDING.
Speak to a licensed electrician. Current from the generator can go into the utility line and electrocute a lineworker.
- Connect each load to the generator with an outdoor extension cord.5mReport a problem with step 1, Start the generator
- Never connect the generator to the wiring of a building.
- Honda states that a connection to a building must isolate generator power from utility lines.
- Speak to a licensed electrician about a transfer switch.
- Start the engine.2mReport a problem with step 2, Start the generator
- Make sure that the position is correct before you start the engine.
LEAVE THE BUILDING IMMEDIATELY IF AN ALARM OPERATES.
Carbon monoxide can make a person unconscious before that person knows about the danger.
- Examine the alarms and the people each hour.2mReport a problem with step 3, Start the generator
- Leave the building immediately if an alarm operates.
- Call the emergency number for a person with a headache or dizziness.
- Record the position that you used.3mReport a problem with step 4, Start the generator
- Put a peg at each corner of the position.
- The next outage is at night and in bad weather.
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- portable generator
- Also called: generator, genny, gennie, backup generator, emergency generator, storm generator, gas generator
- carbon monoxide
- Also called: CO, carbon dioxide, fumes, exhaust fumes, poison gas, the silent killer
- carbon monoxide alarm
- Also called: CO detector, CO alarm, carbon monoxide detector, gas detector, the beeping thing in the hall
- exhaust
- Also called: tailpipe, muffler, exhaust pipe, the hot bit at the back
- power outage
- Also called: power cut, blackout, outage, when the power goes out, lights out
When to use a professional
Never connect a generator to the wiring of a building. Speak to a licensed electrician about a transfer switch. Honda states that a connection to a building must isolate generator power from utility lines and obey local law. Current that goes back into the utility line can electrocute a lineworker.
Stop if you cannot get 20 feet between the generator and every building. Do not decrease the distance. Use a different source of power, or leave the building.
Do not operate a generator in a home, a garage, a basement, a crawlspace or a shed. There is no safe method to do this. An open door does not make the space safe.
Leave the building immediately if an alarm operates. Then call the emergency number for your country. Do not go into the building again until a responder tells you that it is safe.
Call the emergency number for a person with a headache or dizziness near a generator. CDC states that the symptoms are frequently like influenza. Tell the medical staff about the generator.
Common questions
How far from the house does a generator have to be?
CPSC published the number most people are looking for in May 2026: operate generators outdoors only, at least 20 feet from homes and buildings, with exhaust directed away from windows, doors and vents. CDC gives the same 20 feet but measures it differently, saying only use generators outside, more than 20 feet away from any windows, doors, and vents. Those are not in conflict so much as anchored to different things, and the safe reading is to satisfy both: 20 feet from the wall and 20 feet from every opening. Your generator's own manual may ask for more, and if it does, that is the number to use. What you must not do is split the difference with anything shorter.
My generator's manual says three feet. Is CPSC wrong?
Neither is wrong, and this is the most misread pair of numbers on the subject. Honda's published figure is at least three feet from buildings when the engine is running, with at least three feet of clearance on the top and all four sides — and it says plainly what that distance is for: cooling. It is a heat and airflow clearance for the machine, not a distance that protects lungs. The carbon monoxide setback is the CPSC and CDC figure, and it is roughly seven times larger. Satisfying the three-foot cooling clearance does nothing at all about the exhaust.
Can I run the generator in the garage if I leave the door open?
No, and this is the single most common way people die. CPSC's position is that opening doors or windows will not provide enough ventilation to prevent the buildup of lethal levels of carbon monoxide, and its instruction is never to use portable generators indoors or in garages, basements or sheds. CDC says never use a generator inside your home or garage even if doors and windows are open. A garage with the door up is a partially enclosed space, and so is a carport, a porch, a tent, and the space under a deck. There is no version of this that works.
Why is generator exhaust so much more dangerous than a car in the driveway?
Because of how much of it there is. CPSC's comparison is direct: one generator produces as much carbon monoxide as hundreds of cars. That is why the agency describes it as deadly and able to kill you in minutes, and able to incapacitate and kill consumers within minutes. Carbon monoxide is colorless and odorless, so there is no smell to warn you and no moment where you notice it and decide to leave. The symptoms CDC lists — headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion — arrive in an order that makes you less able to act, not more.
Do I need a CO detector if the generator is outside and far away?
Yes. CPSC's instruction is to always have a working carbon monoxide alarm in your house, and CDC specifies a battery-powered or battery backup detector when a generator is in use. The reason the battery matters is obvious once you say it out loud: the reason you are running a generator is that the mains power is off, so a carbon monoxide alarm that only runs on house current is not running. Put one on every level of the home and press the test button before you start the engine, not after.
Is there such a thing as a generator that shuts itself off?
Yes, and it is worth knowing about before you buy. CPSC advises looking for a generator with a carbon monoxide shut-off safety feature, which automatically shuts the machine off when dangerous carbon monoxide levels build nearby. It names two standards that cover this: models meeting PGMA G300-2023 and UL 2201-2023 include carbon monoxide safety technologies, and CPSC notes that UL 2201 certified models have reduced CO emissions in addition to the shut-off feature. A shut-off feature is a second line of defence, not a licence to move the machine closer to the house.
Can I plug the generator into a wall socket to power the house?
No. That is called backfeeding and it is dangerous well beyond your own property. Honda's own safety guidance states that connecting a generator to a building improperly could allow electrical current to feed back into utility lines, creating an electrocution hazard for utility workers, and that connections to a building must isolate generator power from utility lines and comply with all local laws and electrical codes. The legitimate version of what you are trying to do is a transfer switch installed by a licensed electrician. Until you have one, run cords from the machine to the appliances.
What about my neighbour's house — does 20 feet apply to that too?
It does, and people almost never think about it. Carbon monoxide does not know which building it drifts into, and terraced and closely spaced housing puts a neighbour's window well inside the distance CPSC and CDC are talking about. Measure to their walls and openings the same way you measure to your own, and tell them the machine is running. If the only spot that satisfies the distance for your house puts the exhaust at somebody else's bedroom window, it is not a usable spot.
Where exactly does the 20-foot figure come from?
It is CPSC's, published in its hurricane season safety advisory dated 27 May 2026, in the wording quoted throughout this page. We are naming the source rather than presenting the number as general knowledge because the figure has changed over the years and because CDC states it against a different reference point. If you find a shorter distance quoted somewhere, check who published it and when before you use it. We will not print a distance we cannot trace to a federal agency or to a named manufacturer.
Related procedures
- How to get the house ready for a storm and a power outage
- How to clean or change the air filter on a portable generator
- How old is my carbon monoxide detector and when do I replace it
- How do I safely heat my house when the power goes out?
- Find which alarm is chirping and what the chirp means
- Choose an extension cord for a portable generator
- What size generator do I need, and how do I work out running watts and starting watts for the things I want to power?
- Where should I put smoke detectors, and how many do I need
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1CPSC Warns of Generator, Carbon Monoxide and Fire Hazards Ahead of Hurricane Season
- Tier 1Generators and Engine-Driven Tools
- Tier 1Carbon Monoxide Poisoning Basics
- Tier 1Avoiding Carbon Monoxide Poisoning (Natural Disasters PSA toolkit)
- Tier 1Generator Safety
Revision history
Current version 1 · updated 2026-07-29 · next review due 2027-07-29
- v1 · 2026-07-29First draft. Carbon monoxide setback traced to CPSC's hurricane season advisory of 27 May 2026 (at least 20 feet from homes and buildings, exhaust directed away from windows, doors and vents), read 2026-07-29. CDC's 'more than 20 feet away from any windows, doors, and vents' is published alongside it rather than merged, because the figure is the same and the datum is not. Honda's 'at least three feet (one meter) from buildings' is published as what it is — a cooling clearance — and is explicitly not offered as a carbon monoxide distance. No distance is averaged. Enclosed-space operation carries DANGER, which is the level CPSC's own consequence wording demands; nothing on this page is a NOTICE that describes injury. Extension cord sizing and the machine-specific setback publish as consult-the-manufacturer. Refuelling is deliberately out of scope and is not covered here.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.