A system to provide eye or sensor protection from laser-beam damage is investigated. Light beams exceeding a safe energy density are prevented from reaching the observer or sensor by the destruction of a mirror in the line-of-sight. The replaceable mirror consists of a 10- to 20-nm vacuum-deposited metal film on a 2- to 8-micrometer black plastic substrate. The mirror is vaporized directly by focusing the input beam on it. The vaporization, which occurs fast enough to protect against Q-switched lasers, prevents the potentially damaging radiation from reaching the eye or sensor. The energy reflected by various prototype limiting mirrors is measured as a function of the incident energy in an experimental arrangement employing 1-J Q-switched and normal-pulsed ruby, and 2-W CW argon laser beams.