Given the way that unit works, there's little danger of my using the Coleman unit beyond the test. It would take all night to warm the van enough to be noticeable, by that time you've given up on it and found lodging in a motel anyway. It's just way too small for the job, unless you're ice-fishing and want to warm your hand over it occasionally. The Mr. Heat units are rated for indoor use and they're just plain better anyway. Still with cautions all over the place, they use oxygen and so you have to provide ventilation.