I've come across recipes that involve the use of a Butane or Propane torch. Is it safe to use a propane torch bought at the Hardware store, or is there something different about the torches and/or fuel that is sold at a culinary store?
Propane and butane are pure alkanes. They don't produce anything nasty when burned. The worst you could possibly get should be carbon monoxide (and I am not even sure it can be produced in a torch, the dioxide ifs much more likely), but it being a gas, it won't stick to your food. The complex molecules you get from heating the food itself have more potential for being harmful than the combustion products of a propane butane torch. Ago yes, it is food safe.
Another matter of safety is that it is easier to cause a fire with a hardware store torch, because it has more power than the kitchen ones. But a sensible adult should be able to handle the thing safely.
Yes, you will be just fine food safety wise. The Bernzomatic heads available with the triggers are best for convenience. I actually recommend you look for MAP/MAPP gas which will lessen your risk of "torch-taste" but as was mentioned earlier the food safety issue is not a problem, it's the same propane that your grill uses.
A few tips, always start your torch facing away from your food. There will be a small puff of gas initially that you don't want to hit your food. Keep a nice blue hot flame and wave your torn like you were painting brush strokes on a canvas so you don't get hot spots.
I have worked in the metal industry with both products a map gas seems to me more of a mix of what we concidered waste gas where propane butane are as they said a clean burning natural gases I would use and think would be more safe for direct cooking. Also will get you out of a fix when you have left your lunch and have nothing more than a can of soup. Punchure the top and heat. Hell ive even cooked bbq shrimp for the whole crew with nothing more than aluminum foil and a rosebud hook to a propane tank. Got funny looks while doing it but a whole lotta thank you afterwards and when ya gonna do that again? ....."remember cooking is like sex more imagination you put into it the better it is".