These little heaters use a "plenum" or heat exchanger to heat the air and blow it around your camper. They do not interact with outside air, they pull in air from the camper and heat it. If you are feeling warm air from the vent, it may be just reverse transferring from the extreme heat outdoors. IF it is excessive, have a professional look at the unit to make sure the plenum is sealed and not leaking. Dangerous if combustion gases come in when it is actually running.