Common blunders include using the wrong container, wrapping food too tightly, and overlooking critical time and temperature controls. Most people know to avoid metals and foils in a microwave, but may overlook the small metal clip or other bit of metal in a package that can damage the oven. A margarine tub, for example, is likely to warp. Plastics not designed for microwaves may also contain compounds called plasticizers.
Many plastic wraps contain plasticizers, too.
When heated, plasticizers can release harmful chemicals into food. If this happens, it actually represents a type of chemical hazard. Otherwise, you may have a wrap that will leach harmful plastic-related compounds. 2 - Wrap food loosely You should cover food, but not tightly. Always allow a little vent for steam to escape.