Buy a Garage CO Detector NOW
Regardless of all the debate on should it, shouldn't it, I bought a CO detector for my garage.
I've read too many accident reports on aircraft tragedies that absolutely shouldn't have happened because no one could possibly be so stupid or nothing could fail in such a way yet multiple stupid things happened just as multiple things failed.
Cheap insurance.
Luckily my detectors are networked so the alarm sounds in the house too. So if someone (me) is stupid enough to fall asleep in the garage with the car on stop-start and the safety mechanisms are stupid enough not to kick in (they already are), I have one more level of protection.