When using an MR16 Halogen lamp, why do I need to use a closed fixture or an MR16 with cover glass?
MR16 lamps without cover glass should only be used in a closed fixture (fixture that keeps all parts of bulb enclosed) since the filament tube of all MR16 lamps is pressurized. In the unlikely event that the filament tube breaks, the closed fixture keeps glass particles from leaving the fixture. MR16 lamps with a built-on cover glass can be operated in an open fixture since the cover glass will contain any broken pieces of the filament tube.