Entrances to laser areas are to be posted in accord with ANSI standards. In particular, areas where Class 3b or 4 lasers are used must be secured against persons accidentally being exposed to beams, and be provided with a proper warning indication. All windows, doorways, and portals should be covered or restricted to reduce transmitted laser levels below MPE. The Office of Health Physics provides appropriate signs for posting laser areas and advice on controlling laser areas.

The term "proper warning indication" generally means that an illuminated warning sign is outside of the area. Preferably the light should be flashing and lit only when the laser is on. (When a Class 3 or 4 laser is left on and the personnel leave the room, the door shall always be locked.) Lights alone do not suffice as adequate warning, unless the light is clearly posted as to its meaning. A well-designed warning light should have redundancy, e.g., two lights, a "safe" light when the laser is off, or two lamps, wired in parallel, in the "laser on" signal.

Personnel who do not read English language, and who may need to enter areas where lasers are used are to be given appropriate instruction as to the meaning of warning signs and labels. Environmental Health & Safety will assist in obtaining translations of warning signs, which may be needed. The P.I. is responsible for posting signs and informing the personnel.