Engineering Control Measures - Interlocks

Interlocks are safety devices that keep a laser from operating when optical viewers are being used to view the beam path or beam reflection area. Such optical filter interlocks are required for all class lasers except Class 1.

Interlocks that cause beam termination or reduction of the beam to Maximum Permissible Exposure (MPE) levels must be provided on all panels intended to be opened during operation and maintenance of all Class 3M, Class 3B, and Class 4 lasers. The interlocks are usually connected electrically to a beam shutter that automatically closes the shutter and eliminates the possibility of hazardous exposures. Interlocks must be "fail-safe" for embedded Class 3B and Class 4 lasers; that is, they must possess redundant electrical interlocks for each removable panel.

A temporary laser control area should be established when adjustments or service on the laser will cause the safety interlocks to become inoperative or when the laser radiation outside a Class 1 laser protective housing will exceed the MPE limits.

All Class 4 lasers or laser systems are to be provided with a remote interlock connector to allow electrical connections to an emergency master disconnect ("panic button") interlock or to room, door, or fixture interlocks. When open circuited, the interlock shall cause the accessible laser radiation to be maintained below the appropriate MPE level. The remote interlock connector is also recommended for Class 3B lasers.

Such remote interlock connectors are meant to protect against someone accidentally entering a control area when a laser is in operation.

To learn more about LSO visit our Medical Laser Safety Officer Online Training web page.