If you sleep in a garage all night with the propane on, can you die from the fumes?

Last night, my parents got into a huge fight. My dad decided to sleep in the garage, but the garage has no heat. So, he turned the BBQ on and I'm really worried. Could the propane fumes for 8 hours kill him or do any damage? I really don't want to go out there this morning to find him not waking up. ):