Are Kerosene Heaters Safe?

I agree. Blowing up isn’t a good thing. Since kerosene heaters involve open combustion, I wouldn’t used them anywhere near wood dust or flammable vapours, though there won’t be any danger in places where you’ll be using waterborne finishes since they’re not flammable. A bigger problem is the effectiveness of a kerosene heater in your garage. They’re cozy to snuggle up to, but don’t put out a lot of heat when it comes to warming an entire garage (which probably isn’t well insulated). It usually takes something as potent as a woodstove or oil heater to keep a garage warm enough for finishing, but these still present a fire hazard. You might consider waiting until warmer weather to finish your project, or get permission from the house boss to do the work inside. Waterborne urethanes are almost odourless, so you shouldn’t have to beg too hard.