Engineering Control Measures

An effective method for laser accident prevention is to employ engineering controls. Engineering controls are built-in safety features, such as system enclosures, interlocks, and beam stops (automatic shields that block the beam from entering an area). Engineering controls are considered the most reliable because there is less room for human error once they have been successfully implemented.

Protective Housings

Protective housings or enclosures can be as simple as providing PVC tubing along the beam path to encompass most of the laser light, or as elaborate as housing a laser in a chamber and using closed-circuit TV to view the laser in operation.

When a Class 3B or Class 4 laser or laser system is enclosed within a protective housing or protected area enclosure, access should be limited to properly trained individuals. These individuals should only be allowed access when following specific engineering and administrative controls.

Protective Barriers

Windows or entryways that are located within the NHZ of a Class 3B or Class 4 laser system must have an appropriate filter or barrier to reduce transmitted laser radiation to levels below the MPE level. When the MPE level for human skin is exceeded, windows and entryways should be protected with fire retardant material. Note that the flammability and decomposition products of the material should be taken into account when choosing a barrier. It is important that the barrier not support combustion or release toxic airborne contaminants due to exposure to a laser.

Key Controls

All Class 4 lasers and laser systems require a master switch control. The switch can be operated by a key or computer code. When disabled (key or code removed), the laser is not capable of operation. Only authorized system operators should be permitted access to the key or code. Inclusion of the master switch control on Class 3B lasers and laser systems is also recommended but not required.

Warning Systems

An audible tone or bell, or a visual warning (such as a flashing light), is recommended as an area control for Class 3B laser operation. Such a warning system is mandatory for Class 4 lasers. These warning devices should activate upon system start-up and should have a sound distinct to the laser operation.

Beam Pathways

If a high-powered laser's path has been totally embedded within a protective enclosure, then the laser is considered to have an engineering control that prevents beam access during operation and maintenance.

Such a completely-enclosed system, if properly labeled and properly safeguarded with protective housing interlocks (and all other applicable engineering controls), will lower the hazard to that of a Class 1 laser and may be operated in the enclosed manner with no additional controls for the operator.

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