Hi Linda, this is Jim Bunting, Canadian Field Editor, and this subject will be fully covered in an article in our upcoming November edition. I have done some in-depth research of various products, and have come up with an item that will safely, and ecconomically heat either a B-van, or a D-truck interior for a cost of $3 dollars per night. This will not, repeat, not keep the engine warm, but that can be solved with a 100 foot extension cord, and a good block heater. Most buildings have exterior power outlets, and I'll leave the rest to your imagination. Please read our November edition for the details on this great alternative to burning fuel all night, to say nothing of the hours you are taking off the life span of your engine. The item is made in the USA, patented, and is specifically designed for use in enclosed spaces. Got your attention have we? Stay tuned for the November edition. Comments Please.