Years ago, my Dad, little brother, and myself were camping in the mountains during late November. There was snow on the ground and it was cold. We have driven most of the day, had finally reached our camp site late, and had plans to hunt elk the next few days. We crawled into the small pick-up camper, cracked the top vent and proceeded to go to sleep. Somewhere around 6:00 am Dad woke me up complaining of a nasty headache and that he couldn't get his matches to light (to light the lantern); I tried my butane lighter and it would not light either.
We opened the door and both the matches and lighter worked fine!
After we started to regain our composure, we looked inside the camper because we knew we had left the top vent open a small amount and to our surprise, the entire inside of the camper was covered with about a half inch of frost (from our breathes during the night), including the vent opening ... we basically sealed ourselves in a frozen coffin ... I am glad Dad's headache woke him up
My new CT conversion has two roof vents that are always open at night and wide enough to prevent frosting over in cold weather ... AND insulated to reduce the moisture condensation inside.
Be careful, a tight or even nearly tight camper/or tiny trailer can be deadly!