I do not believe that epoxy vapours are flammable, I think that varnish fumes are.  Read that label!  I remember refinishing the floor in my house and that varnish (a polyurethane) was explosive, it recommended that we shut off the pilot light on furnace.  For a small project hist winter, I used the spare room downstairs and periodic venting so that it did not get too cold.  I kept the door closed to minimize that smell in the rest of the house.  Normally I would have waited till spring but this was a Christmas present. 

I personally would not use a flame based heater when varnishing.

Thank you for that tip David.  I have no problem with shutting off the heater prior to varnish.  The garage will retain heat well.  I just need a bump to get above 55.

 Kim

How will you hold the heat with the door open? Ventilation and a respirator are madantory with varnish. Bad stuff.

You may want to wait for warmer weather but before the green pollen starts flying around. There is a small window for the best time to varnish.