We use a butane torch in mycology to flame sterilize our metal tools (scalpel, pick, etc.) before use. Flame sterilization is a very quick way to ensure that your metal tool is free of any possible contaminants. Contamination of your tools can happen throughout mycology processes. That's why having a torch immediately ready it essential.
In order to sterilize a metal tool you would simply heat the tool until it's red hot. Turning red hot isn't necessary since most contaminants die off quickly before that. However, seeing the red is a good visual indicator that the tool is clean. That quick blast of heat (1000-1500 degrees F) instantly kills any bacteria, fungi or any other microorganism.