Hey Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
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smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
Dugger
Senior Member
Offline
The only filters that would effectively stop the motor killing or ignitable dust would be HEPA type and they would just be too much resistance for typical space heater fan.
Better to be cold than to be unsafe.
I believe the best garage heaters are the direct fired (LPG or natural gas - your choice) radiant heaters that are totally enclosed and are real common in commerical garages. All combustible air is drawn from outside as well as the discharge of the combustible products. Another advantage of radiant heaters is there are no fans to recirculate dust/fumes. Only draw back, they are not cheap. I use a portable propane radiant space heater in my garage, I run it during dinner time, and turn it off when I am working - works pretty good, but my garage is well insulated and fairly draft free. Those roll-up metal garage doors (uninsulated) are a huge heat sink and I had to insulate mine for this method to work.
Better to be cold than to be unsafe.
I believe the best garage heaters are the direct fired (LPG or natural gas - your choice) radiant heaters that are totally enclosed and are real common in commerical garages. All combustible air is drawn from outside as well as the discharge of the combustible products. Another advantage of radiant heaters is there are no fans to recirculate dust/fumes. Only draw back, they are not cheap. I use a portable propane radiant space heater in my garage, I run it during dinner time, and turn it off when I am working - works pretty good, but my garage is well insulated and fairly draft free. Those roll-up metal garage doors (uninsulated) are a huge heat sink and I had to insulate mine for this method to work.