NIST Says 25 Feet for Generators; Most Checklists Say 20

TL;DR: Put a portable generator at least 25 feet from the home with exhaust pointed away from windows, doors and vents, following National Institute of Standards and Technology guidance described by Propane Insider.

That 25-foot line is 5 feet farther out than the 20-foot figure printed on most storm checklists. The Propane Insider report “NIST Says 25 Feet for Generators; Most Storm Checklists Still Say 20” states that a customer who parks a unit 20 feet from the house is following common checklists and is still 5 feet short of what the National Institute of Standards and Technology recommends. With weeks of hurricane season left after Oct. 6, 2026, that gap fits directly into pre-storm setup, extension-cord reach, and carbon-monoxide alarm checks.

The 25-foot NIST number

The National Institute of Standards and Technology guidance puts the unit at least 25 feet from the home, with exhaust pointed away from open windows, doors and vents, according to Propane Insider. The same report notes that a generator outside but too close to the home can also be dangerous. A utility safety page reaches the same distance. Generator Safety from CEMC Power, published Oct. 1, 2026, instructs users to position generators at least 25 feet outside the home, away from doors, windows and vents that can allow carbon monoxide to enter the home. CEMC Power also instructs users to install backup carbon monoxide alarms and to keep children and pets away from portable generators at all times. That page adds three equipment rules: ensure the generator is properly grounded, use three-pronged extension cords rated to handle the load, and inspect extension cords for cuts, frays or other damage before use.

Why most checklists still say 20 feet

The 20-foot figure is everywhere in storm material, according to Propane Insider. HurriTrack’s generator guide calls it the general safety guidance, and the storm-safety graphic CBS News Miami published for Floridians says to keep a generator at least 20 feet from doors and windows. Federal checklists repeat that shorter distance. A How to Run a Generator Safely guide published Oct. 3, 2026 summarizes the Consumer Product Safety Commission 2026 hurricane-season warning as requiring operation outdoors only, at least 20 feet from homes and buildings, with exhaust directed away from windows, doors and vents. The same summary describes Ready.gov guidance as requiring generators, camp stoves or charcoal grills always outdoors and at least 20 feet away from windows, including at least 20 feet from windows, doors and attached garages. The Federal Emergency Management Agency generator graphic says only use it outside at least 20 feet from homes and garages, never plug it into a wall outlet or main electrical panel, and keep the exhaust pointed away from the home, according to that Oct. 3 summary.

Never in the garage — even with the door open

On the garage, every source agrees, according to Propane Insider. The National Institute of Standards and Technology says never to put a generator indoors, including a garage, basement or crawlspace, even with doors and windows open. HurriTrack adds that carbon monoxide can build up in a garage and seep into the house with the door open. The Consumer Product Safety Commission says never use a portable generator inside homes, garages, basements, crawlspaces, sheds or other enclosed areas, even if doors or windows are open, according to the Oct. 3 How to Run a Generator Safely summary. That summary cites Occupational Safety and Health Administration guidance that open windows and doors may not prevent carbon monoxide from building up. The BestGenerator carbon-monoxide safety guide updated Oct. 1, 2026 lists the same prohibited spots: never inside a home, garage, basement, crawlspace or shed, even if doors or windows are open, and never in an attached garage even with the door open. The BestGenerator guide adds not to place a unit on a porch, under a carport, or under a deck or overhang because exhaust can collect there and drift inside. The U.S. Consumer Product Safety Commission has warned, “Using a generator can kill you in minutes,” as quoted by CBS News Miami and repeated by Propane Insider. The BestGenerator guide states that one generator produces as much carbon monoxide as hundreds of cars and that the gas cannot be seen or smelled.

What Laura and Ian showed about exhaust

CBS News Miami reports that Hurricane Laura caused 15 deaths in 2020, eight of them from generator carbon monoxide poisoning, according to Propane Insider. In the two weeks after Hurricane Ian hit Florida in 2022, at least 41 people suffered carbon monoxide poisoning, the Tampa Bay Times reported, citing the Florida Department of Health. Before Ian, then-National Weather Service director Ken Graham said storms like Laura had produced more deaths from generators afterward than from storm surge of 16 to 18 feet, according to Propane Insider. The Consumer Product Safety Commission 2026 hurricane-season warning calls portable generators one of the leading causes of post-storm carbon monoxide deaths and calls carbon monoxide a colorless, odorless gas that can kill within minutes, according to the Oct. 3 How to Run a Generator Safely summary. Centers for Disease Control and Prevention symptom information reproduced in the BestGenerator guide lists headache, dizziness, weakness, upset stomach or vomiting, chest pain and confusion, often described as flu-like. The same guide states that people who are asleep, drunk or under the influence can die from carbon monoxide before having symptoms. If anyone feels dizzy, sick or has a headache, the BestGenerator guide instructs users to get everyone into fresh air and call 911. If a carbon-monoxide alarm sounds, the same guide says to get everyone outside to fresh air right away, then call 911. The Propane Insider report gives the same response: if a battery-powered alarm sounds, everyone gets outside to fresh air and calls for emergency help.

Cords, transfer switches and backfeeding

HurriTrack warns against backfeeding, which it describes as connecting a generator directly to household wiring without a properly installed transfer switch, according to Propane Insider. The Federal Emergency Management Agency says never plug a generator into a wall outlet, according to the Oct. 3 How to Run a Generator Safely summary. That summary states that connecting a set to house wiring, instead of plugging appliances in with a heavy-duty cord, needs a transfer switch installed by a licensed electrician and a permit where local code requires one. CEMC Power states not to connect generators directly into household wiring unless an appropriate transfer switch is installed, warning that power can backfeed along power lines and electrocute utility lineworkers making repairs. The BestGenerator guide instructs users to plug appliances straight into the generator or use heavy-duty, outdoor-rated, three-prong cords, and to check cords for cuts first. The Consumer Product Safety Commission portable-generator safety alert says to connect appliances with heavy-duty extension cords designed for outdoor use, with a wattage rating that exceeds the total of everything plugged into them, according to a Benchlet hurricane-season generator guide published Oct. 1, 2026. The same Benchlet guide says never to power house wiring by plugging the generator into a wall outlet, a practice called backfeeding, because it creates an electrocution risk for utility workers and neighbors served by the same transformer.

Alarms, fuel, rain and shutdown extras

The Consumer Product Safety Commission recommends battery-operated carbon-monoxide alarms, or plug-in alarms with battery backup, outside sleeping areas and on each floor of the home, and testing them monthly, according to the Benchlet guide. The BestGenerator guide states to put a carbon-monoxide alarm on every level of the home, follow the maker’s instructions for placement and mounting height, test alarms monthly, and use battery or battery-backup alarms because a plug-in-only alarm will not work in an outage. The Centers for Disease Control and Prevention adds that interconnected alarms are best because when one sounds they all sound, according to the GeneratorWiki safety checklist summarized in search results and consistent with the BestGenerator account. For heat and fuel, the National Fire Protection Association says never refuel while the generator is hot, and Ready.gov and Occupational Safety and Health Administration guidance warn that fuel spilled on hot engine parts can ignite, according to the BestGenerator guide. The Consumer Product Safety Commission says never to store generator fuel in the home and places gasoline, propane, kerosene and other flammable liquids outside living areas in properly labeled, non-glass safety containers, according to the Benchlet guide. For wet weather, Occupational Safety and Health Administration guidance says to keep a generator dry and not use it in rain or wet conditions, and to protect it with a canopy if needed, according to the BestGenerator guide. That guide states to use a vented cover made for running generators, or an open canopy, out in the open 20-plus feet from the house, and never move the generator into a garage, shed, carport or onto a porch to keep it dry. CEMC Power adds not to open windows or doors while the generator is running, not to rely on generators as a full-time power source, and not to overload generators beyond essential equipment. For buyers, the Consumer Product Safety Commission urges buyers to look for portable generators with a carbon-monoxide shut-off feature, and notes that models certified to PGMA G300-2023 and UL 2201-2023 include carbon-monoxide safety technologies, according to the BestGenerator guide. That guide states the shut-off was not required by federal rule as of October 2026, with a supplemental proposal published April 20, 2023 and no final rule found in the Federal Register as of Sept. 30, 2026. Propane leak awareness is separate from carbon-monoxide detection: if occupants smell gas, Propane Education & Research Council advice reproduced by Propane Insider is to put out any flame, leave light switches and phones alone inside, get everyone out right away, then call the supplier’s office from a safe place, or the fire department if they cannot reach the supplier or anything looks dangerous.