Melting process and temperatures depend on the type of plastic.
For safety, people recommend face mask. I just hold breath however.
Another safety measure is googles. Eyes are very important.
Need to be careful to prevent overheating (burning).
Temperatures are as follows:
Polyethylene: 130-140 C
Ways to melt plastic
Good to bend hard plastic. Under heat gun, it becomes very flexible.
Good for plastic film (wrap).
Don't use the same oven as for cooking food. Plastic particles could be poisonous.
With fire, there should be a layer of additional metal can between fire and plastic per se. Otherwise plastic could burn.