In many campus research areas the requirements for controlled laser areas have been interpreted to mean that the doors must be locked, or interlocked, and a proper warning indication provided at the entrance to the area when the laser is operating, unless the area just inside the door is protected by a barrier as described below. Also proper protective eyewear must be available at or immediately outside of the entrance.

For Class 4 lasers that have unenclosed beam lines, the ANSI Standards call for interlocked doors (or sensors or pressure sensitive doormats, etc.), or devices that turn-off or attenuate the laser beam in the event of an unexpected entry into an area. An alternative method of protection is to provide a suitable barrier (screen or curtain) just inside the door or wherever most appropriate to intercept a beam or scatter so that a person entering the room cannot be exposed above the MPE limits.

Procedural methods may be used to control entry as an alternative to engineered interlocks, provided the above conditions are met and all personnel have been trained in laser safety, and protective equipment is provided upon entry. In general, access from public corridors cannot be controlled by procedures, as the public normally would not be trained in the necessary safety procedures.

Other conditions related to control of laser areas include the following:

• Keep the exposure at the entryway below MPE by use of a barrier inside of the door. Don't direct the laser beam toward the entry.
• Use shields and barriers around the laser work area so that the beam, reflections and scatter are contained on the optical table. Try to keep the unenclosed beam path out of the normal eye-level zone. (The normal eye-level range is from 4 - 6 feet from the floor.)
• Ensure that only diffuse reflective materials are in or near the beam path to minimize the chance of specular reflections.
• Ensure that locks or interlocks do not obstruct rapid egress from the door or the admittance to the room in the event of an emergency situation.
• Have lighted, warning signs (preferably flashing) and/or audible signals to indicate when a Class 4 laser is energized and operating. Signage must clearly explain the meaning of the lights.

Unauthorized persons are to be prevented from entering an area, if the beam is not contained, i.e., areas at the room entrance may exceed MPE. Locks or electric door locks can be used to secure the room (access to the room should still be available by key or an override switch, egress should not be impeded). Locks and warning lights should activate when the the laser is "ON." It is always essential that the locks not impede exit from the room, and provide for entry in case of fire or emergency; hence, slide bolts and dead bolts are not acceptable locks.

Many laser systems have a connection for room interlocks, which can serve as a mechanism to link warnings and door locks to laser operation. The connections can also be used for door interlocks (to shut off the laser) or to operate solenoid switches to ditch the beam into a stopper if the door is opened. Momentary by-passes and timers can be used to permit controlled entry. The lines between the laser and warnings and locks system should be low voltages. Also, users shall inspect the warning and access control systems periodically as a part of the overall safety program.

Laser areas shall be designed so that beams cannot exit from the area at levels exceeding MPE. Provide suitable barriers or cover windows with materials that will attenuate the beam. Check for leakage of stray beams around doors or barriers.

A checklist of applicability of protective measures according to ANSI classes 3 and 4 may be found in Appendix D.