How do you use a generator or heater safely in an emergency?

Short answer. Run a portable generator outdoors only, at least 20 feet (about 6 m) from doors, windows and vents, and never inside a home, garage, basement, carport or shed, even with windows open ²⁴. Install battery-powered or battery-backup carbon monoxide (CO) alarms on every level of the home ⁵. In the United States, about 100 people die each year from CO poisoning linked to portable generators ⁴.

Why is carbon monoxide the main danger during a power outage?

Ready.gov describes carbon monoxide as a colorless, odorless gas that can kill you, your family and pets ⁵. You cannot see or smell it: Health Canada notes that it can only be detected with a CO alarm ⁸. Generators and other fuel-burning equipment produce it, and using them indoors or in poorly ventilated areas can expose people to dangerous levels ⁸.

The toll is not small. CDC reports that each year in the United States more than 400 people die from unintentional CO poisoning not linked to fires, more than 100,000 visit an emergency department and more than 14,000 are hospitalized ¹. CPSC estimates an average of about 100 deaths a year from portable generators alone ⁴. Health Canada notes that using these appliances during a power outage can cause dangerous levels of CO to build up indoors ⁸.

Where can a generator safely run?

Outside, and well away from the building. The agencies agree on the principle; the U.S. agencies add a number:

Twenty feet is a minimum, not a target. CPSC also advises closing nearby windows and sealing vent openings near the generator ⁴.

What about heaters, stoves and grills?

The same gas comes from anything that burns fuel. CDC lists generators, grills and other gasoline-, propane- or charcoal-burning devices as items never to use inside a home, garage or carport, or near doors, windows or vents ². Specific points from the agencies:

• Gas oven or stovetop: do not use it to heat the home; it increases the risk of CO poisoning ⁵. CDC says the same: "Don't heat home with gas oven" ².
• Grills and camping stoves: do not grill inside ²; the NHS adds: do not use a barbecue or camping stove indoors or inside a tent ⁶.
• Vehicles and engines: do not leave vehicles or other engines running in enclosed spaces such as a garage ⁶.
• Furnace and appliance vents: after snow, clear outside vents for fuel-burning appliances such as furnaces ⁴.
• Electric space heaters: these do not burn fuel, but they are a fire risk. CPSC asks for at least 3 feet of clearance on all sides from beds, clothes, curtains, papers and sofas, and says to plug them into a wall outlet, never a power strip, and never run the cord under rugs ⁴.

If your home is damaged and cannot be heated safely, CDC advises staying with friends or family or in a shelter ².

Where should CO alarms go?

Agencies phrase placement slightly differently:

• CPSC: on each level and outside separate sleeping areas, interconnected where possible; test monthly and replace batteries if needed ⁴.
• Ready.gov: working detectors with battery backup in central locations on every level of the home ⁵.
• CDC: install a battery-operated CO detector ³.
• NHS: an alarm that makes a loud sound, in each room with a gas, oil, coal or wood appliance ⁶.
• HSENI: battery-powered alarms inside the home, placed according to the manufacturer's instructions ⁷.

Battery power matters for one simple reason: a mains-only alarm goes silent in the very outage that sends people to their generators. If a CO alarm sounds, CPSC says to get outside immediately, then call 911 ⁴. Health Canada also says to leave immediately ⁸.

What are the symptoms of carbon monoxide poisoning?

CDC lists headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion, symptoms often described as "flu-like" ¹. The NHS adds tiredness, chest and muscle pain, shortness of breath and loss of vision ⁶. Two clues point to CO rather than illness: symptoms that come and go, and symptoms that get worse in a particular room or building and improve when you leave or go outside ⁶.

CPSC warns that people may become unconscious before they recognize nausea, dizziness or weakness ⁴. Everyone is at risk, but infants, older people and people with chronic heart disease, anemia or breathing problems are more likely to get sick ¹.

What should you do if you suspect CO poisoning?

1. Stop using the appliance you suspect, if you can do so on the way out ⁶.
2. Get everyone outside into fresh air ⁴⁶.
3. Call emergency services: 911 in North America ⁴; in the UK, 999 or A&E for difficulty breathing, sudden confusion, weakness, chest or muscle pain, or loss of consciousness, and do not drive yourself ⁶.
4. Do not go back into the building until you have received advice ⁶.

Can a generator be plugged into the house wiring?

HSENI advises against it. It warns that connecting a generator to your home could cause a surge in electricity that might result in injury or death ⁷, and advises connecting appliances with heavy-duty extension cords and keeping the connected load within the generator's rating ⁷.

What about fuel?

HSENI advises keeping and fuelling the generator outside, not storing its fuel in the house, and turning it off and letting it cool before refuelling, because petrol spilled on hot engine parts can ignite ⁷.

What official agencies recommend

• United States: CDC, CPSC and Ready.gov all use the same 20-foot minimum ²³⁴⁵. CPSC is the strictest on location, ruling out porches and carports as too close ⁴, and notes that generator models certified to the PGMA G300-2018 and UL 2201 standards, which include CO shut-off features, are estimated to reduce CO deaths by 87% and 100% respectively ⁴. That is an agency estimate for those standards, not a guarantee for any individual unit.
• United Kingdom: HSENI (Northern Ireland) gives no distance in feet or metres; it says not to run a generator indoors, in partially enclosed spaces, or near open doors and windows ⁷. The NHS focuses on alarms and symptoms and lists portable generators among appliances that can produce CO ⁶.
• Canada: Health Canada's overview stresses that a CO alarm is the only way to detect the gas and that generators should not be used indoors or in poorly ventilated areas ⁸; it does not state a distance on that page.

Where a figure is given, it is 20 feet; no agency we reviewed recommends a shorter distance.

Frequently asked questions

Is it safe to run a generator in the garage with the door open?

No. CPSC lists the garage among spaces where a generator must never run, and says opening doors and windows does not give enough ventilation to prevent lethal CO buildup ⁴. Ready.gov also asks for 20 feet from attached garages ⁵.

How far from the house should a generator be?

At least 20 feet (about 6 m) from doors, windows and vents, according to CDC ², CPSC ⁴ and Ready.gov ⁵. Point the exhaust away from buildings ⁴.

Can I warm the house with my gas oven during an outage?

No. Ready.gov says using a gas stove or oven to heat your home increases the risk of CO poisoning ⁵, and CDC gives the same advice ².

Do I need a CO alarm if I only run the generator outside?

Yes. Exhaust can still reach the house, and CO cannot be detected without an alarm ⁸. U.S. agencies recommend battery-backed alarms on every level of the home ⁴⁵.

Who is most at risk?

Everyone can be poisoned, but infants, older people and people with heart disease, anemia or breathing problems are more likely to get sick ¹. CPSC warns that people may lose consciousness before noticing symptoms ⁴.

Build it into your plan

Where the generator will stand, where the alarms go and who checks them belongs in your household emergency plan, decided before the outage. The Phaenyx personal plan ($29 free for a limited time) helps you write down those decisions for your home and your country's official guidance. Build your Phaenyx plan.

Sources

1. Centers for Disease Control and Prevention (CDC) — Carbon Monoxide Poisoning Basics — https://www.cdc.gov/carbon-monoxide/about/index.html (accessed 2026-10-20)
2. Centers for Disease Control and Prevention (CDC) — Avoiding Carbon Monoxide Poisoning — https://www.cdc.gov/natural-disasters/psa-toolkit/avoiding-carbon-monoxide-poisoning.html (accessed 2026-10-20)
3. Centers for Disease Control and Prevention (CDC) — Prevent Carbon Monoxide Poisoning — https://www.cdc.gov/natural-disasters/psa-toolkit/prevent-carbon-monoxide-poisoning.html (accessed 2026-10-20)
4. U.S. Consumer Product Safety Commission (CPSC) — As Winter Weather Impacts Millions, CPSC Issues Safety Tips to Help Families Prevent Carbon Monoxide Poisoning and Fires (3 January 2025) — https://cpsc.gov/Newsroom/News-Releases/2025/As-Winter-Weather-Impacts-Millions-CPSC-Issues-Safety-Tips-to-Help-Families-Prevent-Carbon-Monoxide-Poisoning-and-Fires (accessed 2026-10-20)
5. Ready.gov (FEMA) — Power Outages — https://www.ready.gov/power-outages (accessed 2026-10-20)
6. NHS — Carbon monoxide poisoning — https://www.nhs.uk/conditions/carbon-monoxide-poisoning/ (accessed 2026-10-20)
7. Health and Safety Executive for Northern Ireland (HSENI) — Safety Tips – Using a portable generator in an emergency (26 January 2025) — https://hseni.gov.uk/news/safety-tips-using-portable-generator-emergency (accessed 2026-10-20)
8. Health Canada — Carbon monoxide: Overview — https://www.canada.ca/en/health-canada/services/air-quality/indoor-air-contaminants/keep-carbon-monoxide-out-your-home.html (accessed 2026-10-20)