Running in garage or enclosure...........Have seen end poorly at least a half dozens times........people under estimate how hot the exhaust gets over a long runtime and how much CO generators produce. They run rich compared to other small engines so they don’t surge or gallop.
Occasion one: portable gen set up to run on an auto transfer switch, power goes out, gen comes online. Easy. Gen was in the garage, along with the car, normal garage stuff, and water heater. Power went out, gen came on, ran for several hours, overheated one of the car's tires, caught fire, burned the garage and part of the house.
Occasion two. Similar setup, in garage. Power goes out, gen comes online. Overhead door down. Fills house with CO, 2 occupants die during their sleep. This was a high dollar Honda that doesn't make a lot of noise. The 2 occupants never knew what was going on.
CO is heavier than air and tends to hang around the floor. Grab a CO meter and go start the car in the shop, just for a few seconds, and then turn it off. Watch the CO meter change from arms length high, to the floor-it'll be higher at the floors. CO is not the only compound from IC engines...theres CO2, and a TON of other gases-most are nonflammable, which if you have a water heater in the garage, I've seen the pilot light go out because there was no oxygen to sustain combustion. Even had a call once from someone said that if they run their gen for a bit, then start the car, the car will run but poorly. Inside the garage nonetheless. Hmm...must have been a "college graduate".
If you have a portable genset, keep it inside when not in use, but when you need to use it, park it outside. Away from the house. That's why it's portable. If you don't like the portable thing and it's downfalls, you're going to have to invest in a whole-home genset that is fixed. That is the only safe way to do it.
Latest one...guy had a 5500w JD genset that he kept in the truck bed for his primitive camping excursions. Guy was out in an area where daylight had to be pumped into (camping), woke up in the morning for coffee and breakfast, fired up the generator-that noisy thing-and had his breakfast. Started to rain. So he throws a tarp over the truck bed, seals it up pretty good with rubber straps to "keep the rain off of the generator since electricity and water don't mix well", proceeds to burn the truck to the ground along with the camper. Plastic bedliner and hot exhaust started the whole process. His family called me at work asking if I'd heard from him...nope...I was headed that direction after work, so I stopped in, found the burned truck & camper, no sign of him or even any body parts...found him up the road walking toward town. Thankfully he's ok but I think he learned a lesson.
These things are dangerous...extremely...and people tend to downplay what they can and WILL do. Don't play around. If you have a HINT of a doubt, just quit while you're still alive, even if that means spending a little more on a fixed whole-home genset that is specifically designed for what you're wanting to do. I don't particularly care to pick up dead bodies, especially knowing that they KNEW what they were doing was fixin' to kill 'em.
At the least, you can build a small "pole-barn" to house the portable genset permanentaly, but don't enclose it..leave the sides open so cooling air can get INTO the engine and hot air can escape...
On and by the way I have been a victim of CO poisoning. Age 9, don't remember what happened prior to the accident, but I was behind a boat in a raft, boat running stationary. My mom tells how she found me, basically slumped over the side of the raft almost in the water. Nonresponsive. Her and dad nabbed me up, took me to hospital, basically dead. Obviously revived, but not fully...to this day, have lost some vision, some brain function mostly affecting the left side (eye, ear, smell, some feeling lost in left extremities). THAT is what CO and other exhaust gases can do....by the way I'm told that I was in the hospital for 4 weeks being monitored & tested. They say I'm quite lucky....THANKFULLY I don't remember a thing of it.
