An incandescent light bulb is any device that utilizes electricity to heat a filament (or wire) until it glows white. The metal filament would self-destruct long before it reached that temperature if the process were carried out in the open air where oxygen is present. Incandescent bulbs can produce light because the heated filament is contained inside an evacuated glass shell or globe that is either left empty or filled with an inert gas. A vacuum prevents the wire from igniting, and if the sole gas within the bulb is inert, the wire cannot ignite either.