Run a generator outdoors, 20+ feet from windows
Added
During a power outage, use a generator only outside and at least 20 feet from windows, doors and attached garages, and keep it dry. Connect appliances with heavy-duty extension cords, let it cool before refueling, and have battery-backup carbon monoxide detectors on every level of your home.
The result
Result: Ready.gov: generators, camp stoves and charcoal grills should always be used outdoors and at least 20 feet away from windows; never use a gas stove or oven to heat your home.
Note: Carbon monoxide is odorless and can kill. Follow your generator's manual, and get to fresh air and call 911 if a CO alarm sounds.
Source
Ready.gov: Power Outages (opens the original source in a new tab). Check it for the latest numbers before you act.