What is a metal halide light?
The working component of a metal halide bulb – also referred to as a “lamp” – is the arc tube. An arc tube is a sealed glass tube containing electrodes and a mixture of pressurized gases, such as argon and mercury. It’s this part of the bulb that can explode. And when it does, the arc tube breaks the outside envelope of the bulb, spewing hot glass everywhere. The light fixtures that hold the bulb come in two types, open and closed. As its name suggests, a closed light fixture completely encloses the bulb in a “lamp containment barrier” intended to trap the hot glass from an exploding bulb and prevent it from escaping and causing a fire. The lamp containment barrier is the lens on the bottom of the fixture, which is made from acrylic plastic. Unfortunately, acrylic burns, and if hot glass fragments ignite the acrylic lens, burning plastic may drip onto combustible materials and cause a fire. There are better options than acrylic plastic. Polycarbonate plastic, for example, is much less
