The generator rule that prevents carbon monoxide deaths—how far it really needs to be from the house
Every major storm season, the same pattern repeats: the power fails, the portable generators come out, and carbon monoxide quietly starts to build where it should not. You hear the rule of thumb about keeping a generator “far enough” from the house, but the distance that actually keeps exhaust out of your lungs is more precise, and more complicated, than a single number suggests. If you rely on backup power, you need to understand how far is truly safe, how wind and walls change the equation, and why the wrong setup can turn a lifesaving machine into a lethal one.
Why distance is your first line of defense
When you run a gasoline generator, you are essentially parking a small engine in your yard and piping exhaust into the air, and that exhaust is loaded with carbon monoxide. The gas is colorless and odorless, which is why it is often called a silent killer, and it can accumulate in enclosed or semi-enclosed spaces long before you notice symptoms. Safety agencies stress that portable generators are useful only when you treat them as outdoor equipment and keep them well away from doors, windows, vents, and any other opening where fumes can drift back inside.
Guidance for homeowners has converged on a simple baseline: keep a portable generator at least 20 feet from any building and away from openings where exhaust can be pulled indoors. Local officials in Somerville, New Jersey, tell residents to Use portable generators outdoors in well ventilated areas at least 20 feet (7 metres) from windows, doors, and vents, and the Washington State Department of Health echoes that gas powered units should be at least 20 feet away from buildings, noting that Generator Safety still depends on airflow even at that distance. New Orleans emergency planners go a step further, urging you to follow the 20-20-20 rule during outages, which means you Keep generators 20 feet away from the house, direct exhaust 20 feet away from doors and windows, and use a working carbon monoxide alarm.
Why 20 feet is not always enough
The 20 foot guideline is a starting point, not a guarantee, because carbon monoxide does not travel in a straight, predictable line. Wind, walls, fences, and roof overhangs can trap exhaust and push it back toward your siding, then into cracks and vents. Testing has shown that even when a generator is placed 15 feet away, exhaust can still find its way into a structure, especially if it is near a garage, shed, or other barrier that channels fumes. One manufacturer-backed analysis notes that Even 15 feet away was not enough to prevent dangerous concentrations when the unit sat near a wall, garage, shed, or other structure that altered airflow.
That reality is driving a shift toward more conservative advice. After deadly incidents in the days following Hurricane Ida, the Consumer Product Safety Commission and Louisiana State Fire Marshal highlighted that Most municipalities require stationary generators, which power entire homes, to be installed at least 5 feet from openings and 3 feet from combustible materials, and they underscored that portable units can be even riskier because people move them closer than they should. A newer federal warning goes further, urging homeowners to Keep generators 25 feet from homes after a 32 page CPSC report detailed how carbon monoxide, described as a “silent killer,” can enter through windows and vents even when a unit is outside.
How to place a portable generator safely in the real world
In practice, you are often working with a cramped driveway, a small yard, or a crowded patio, which makes the neat radius on a safety diagram harder to achieve. The safest approach is to treat 20 feet as the bare minimum and aim for 25 feet or more whenever your lot allows, then think in three dimensions about where the exhaust plume will go. You want the muffler pointed away from the house, away from neighbors’ windows, and away from any detached garage or shed that could trap fumes, not tucked into a corner that feels convenient.
Some manufacturers emphasize that portable generators are a smart backup only when you run them outside, far from openings, and away from combustibles, and they offer tools like a Generator Safety Checklist to help you verify that distance and clearance. Texas regulators advise that when you are How to safely set up and run your portable generator includes placing it outdoors, away from doors and windows, on a dry surface where exhaust can dissipate. Another Texas guide on Using a generator stresses that you should Stay alert to Signs of Carbon monoxide, such as headache and dizziness, and never refuel while the engine is hot, which is why it reminds you to Add fuel when it is cool.
The rules that never change: indoors is never safe
No matter how bad the weather or how tempting the shelter, the rule against running a generator indoors does not bend. Federal safety officials repeat that you must In the case of a power outage, follow these important life saving tips, which start with NEVER operating a portable generator inside a home, garage, basement, crawlspace, shed, or on a porch, because carbon monoxide can build up and linger even after the engine shuts off. A separate hurricane season advisory frames it under the heading Loss of Power, explaining that Using a generator Safely means NEVER running it in any enclosed space and choosing models with a CO shut off safety feature that can stop the engine if exhaust levels spike.
State fire officials in Connecticut are just as blunt, warning residents in capital letters: DO NOT use a generator indoors because Carbon Monoxide can accumulate quickly and CAN KILL YOU IN MINUTES, a reminder that YOU may have only MINUTES to react before losing consciousness. Local health departments reinforce that message by telling you to keep generators outside and to install carbon monoxide alarms on every level of your home, since In recent years, there has been an increased effort in the United States to prevent poisoning through promotion of residential CO detectors. That research underscores that detectors should be placed according to manufacturer instructions rather than myths about whether carbon monoxide is heavier or lighter than air.
Stationary generators, storms, and the new 25 foot mindset
Whole house standby units follow different installation codes, but they are part of the same carbon monoxide story. A detailed CPSC analysis of stationary equipment found that Staff concluded addressing the CO poisoning hazard associated with these systems is urgently needed, because exhaust can still infiltrate homes through vents and soffits if clearances are ignored. That is why Most municipalities require stationary generators to sit a specific distance from openings and combustibles, and why you should never treat a permanent unit as a license to forget about airflow.
Storm seasons are when these rules are tested, because outages are long and tempers are short. Federal officials have used recent tropical systems to repeat that you must treat every generator, portable or stationary, as a potential source of lethal exhaust and keep it as far from living spaces as your property allows. During hurricane briefings, they have folded generator advice into broader storm guidance, reminding people that Using a generator Safely is as critical as boarding up windows. Local emergency managers in New Orleans, who urge residents to Keep generators 20 feet away and pair them with working alarms, are effectively pushing homeowners toward the same 25 foot mindset that federal regulators now promote.
Layering protection: alarms, airflow, and small habits that matter
Distance is the headline rule, but it is not the only one that keeps you safe. You also need working carbon monoxide alarms on every level of your home and outside sleeping areas, because you will not smell trouble coming. The City of Webster in Texas highlights that The CDC advises you to When using a generator, rely on a battery powered or battery backup CO detector and to measure the 15 to 20 foot distance from the exhaust system to the building if space is tight. Washington health officials caution that Gas powered generators should be at least 20 feet away and Even then, wind can push exhaust back toward your home, which is why they stress keeping windows closed on the side of the house closest to the unit.
Small operating habits also make a difference. Texas safety tips on Using a generator remind you to Stay aware of Signs of Carbon monoxide and to Add fuel when it is cool to avoid fires, while local guidance in Somerville tells you to Use portable generators outdoors on level ground with cords rated for outdoor use. Manufacturers and safety agencies alike emphasize that portable generators are a smart backup only when you follow a checklist that keeps them outside, away from structures and combustibles, and that you never improvise by cracking a garage door or running a unit under an awning just to keep it dry. If you treat the 20 to 25 foot buffer as nonnegotiable, pair it with alarms, and respect the “never indoors” rule, you give yourself the power you need without inviting carbon monoxide into the place you are trying to protect.
