Cabin heater question

[sphanna]

I am wondering if any of you have used a small catalytic heater that is advertised safe for indoor tent, etc. usage to serve as a heater in Model A. My concerns are not so much about using up O2 as to the water vapor combustion product. I am afraid to spend money for this only to find that the water vapor would fog up the windows so much as to be impractical. What do you think? Is my cabin fever causing me to imagine vain things?