Portable generators are responsible for more carbon monoxide deaths than any other engine-driven consumer tool — the placement rules here matter as much as any spec on the generator itself.
The 20-foot rule, and why "cracking the garage door" doesn't work
The CDC and CPSC are consistent and specific: run a portable generator outdoors, more than 20 feet away from your home, garage, shed, or any other occupied structure, with the exhaust pointed away from doors, windows, and vents. This isn't a rough suggestion with flexibility built in — carbon monoxide is colorless and odorless, can build to dangerous levels within minutes, and can render someone unconscious before they notice symptoms like nausea, dizziness, or weakness.
A specific, common mistake worth naming directly: running a generator in a garage with the door open does not provide adequate protection. Exhaust can still accumulate in the garage and drift into attached living spaces regardless of an open door, and CPSC guidance explicitly warns against this. The same goes for porches and carports — a roof and nearby walls can trap or redirect exhaust back toward the home rather than dispersing it safely, so these are not considered safe generator locations either, even though they're technically "outdoors."
Newer generators include real automatic safety technology
Portable generators certified to the current safety standards (referenced as PGMA G300-2023 and UL 2201-2023) include a carbon monoxide shutoff feature that automatically powers down the generator if dangerous CO levels build up nearby, and UL 2201-certified models also reduce CO emissions at the source. This is a genuine, meaningful safety upgrade over older generator designs without this feature, and checking for certification to these current standards is worth doing specifically, not just checking that a generator is "certified" in some generic sense.
Wattage sizing is about starting watts, not just running watts
Similar to a portable power station, appliances with a motor or compressor need a brief surge of starting power well above their steady running wattage — a refrigerator or well pump, for instance. Adding up only the running wattage of intended appliances and matching that to a generator's rated output can mean the generator fails to actually start something with a real starting-watt spike, even though its running wattage alone would have been sufficient. Checking both figures against a generator's rated starting and running watts avoids this mismatch.
The one thing people forget
Install working carbon monoxide alarms in the home, with battery backup, regardless of how carefully a generator is positioned outdoors — CO alarms are a real, independent backup layer of protection, catching a dangerous buildup that could occur due to wind direction, an unexpectedly placed vent, or simple human error in generator placement, precisely the kind of real-world variable that a fixed distance rule alone can't fully account for.