https://sanctioned-suicide.net/threads/i-failed-with-co-method-last-night.25448/
The car won't catch fire as you're bringing in the coals once the flames have stopped.
You're putting the coals in a tray/bucket on bricks or above a water trough so heat danger is minimal.
There should be no smoke. Remember you're bringing in the coals after the smoke and flames have finished outside.
Disposable bbqs smell due to charcoal being impregnated with firelighters but I found a bucket of briquettes had no smell to them at all. Next day the car was fine.
But your last concern is indeed a real concern, and the biggest danger of the CO method. My attempt failed two weeks ago and I'm feeling foggy, slower, headaches etc.
What's more concerning is that harsher side effects can kick in 4-5 weeks after the attempt, as the neurological impact is delayed in 40% of survivors.
Still debating whether to try this again as the actual experience wasn't bad, just the waking up from it!