And don’t put your pets in the overhead bin. People have done this (without the flight attendants even noticing) to find that their pet has suffocated in-flight.
You'd have to be spectacularly stupid to do that. The case I heard where that happened the flight attendant it there, without realizing there was a pet in the container. (the family told her, but somehow she didn't hear or understand)
Obviously a bad idea, but are the overhead bins airtight?
They're not airtight, but without ventilation, CO2 will build up.