i used green house heaters in my van for a few years no probs, until the really bad freeze of two years ago, or was it three when it went down to the minus 10 mark, that froze my pressure wash and killed it, but it was an exceptional year. i then bought an halogen heater which is safer and cheaper and works perfect, obviously with a timer attached and with care where its placed. the problem with the paraffin/greenhouse heaters is soot residue which builds up inside your van a tad!!!!!! now i have the carpet cleaner im simply bringing it inside, full stop, also the wand!!!!!