My shop is only 36-28 so a small wall mounted gas unvented radiant heater on a remote thermostat keeps my garage as warm as I want it rather cheaply in PA Winter weather. I installed a nice big ceiling exhaust fan years ago so I can easily freshen the air in my shop or flip on while running the race cars in the shop (especially with alcohol). I always keep a carbon monoxide tester sitting on top my drill press and it has warned me lots of times over the years.