Engineering Controls - Protective Housing

A protective housing is a physical barrier preventing laser radiation in excess of the MPE from exiting the laser.

 Laser Use without Protective Housing

In some circumstances such as research and development and during the manufacture of lasers, operation of laser or laser systems without a protective housing may become necessary. In such cases the LSO shall determine the hazard and ensure that controls are instituted appropriate to the class of maximum accessible emission to ensure safe operation. These controls may include, but not be limited to:

1. access restriction

2. eye protection

3. area controls

4. barriers, shrouds, beam stops etc.

5. administrative and procedural controls

6. education and training

Interlocks on Removable Protective Housings

Protective housings will have an interlock system which is activated when the protective housing is opened during operation and maintenance. The interlock prevents exposure to laser radiation above the MPE. 

Service Access Panels

Service access panel which are portions of the protective housing and are intended to be removed only by service personnel, permit direct access to laser radiation. They must either:

1. be interlocked (fail-safe interlock not required);

2. require a tool for removal and shall have an appropriate warning label.

Master Switch

A master switch is a key or coded access (such as a computer code) required to operate the laser. 

Viewing Portals and Display Screens

All viewing portals and or display screens included as an integral part of a laser shall incorporate a suitable means (such as interlocks, filters, attenuators) to maintain the laser radiation at the viewing position at or below the applicable MPE for all conditions of operations and maintenance. 

Collecting Accessory

All collecting optics (such as lenses, telescopes, microscopes, endoscopes, etc.) intended for viewing use with a laser shall incorporate suitable means (such as interlocks, filters, attenuators) to maintain the laser radiation transmitted through the collecting optics to levels at or below the appropriate MPE, under all conditions of operation and maintenance.

 Beam Paths

Control of the laser beam path shall be accomplished as described in the following sections.

Totally Unenclosed Beam Path

Where the entire beam path is unenclosed a laser hazard analysis shall be effected by the LSO to establish the NHZ if not furnished by the manufacturer or available as part of the classification. 

Limited Open Beam Path

Where the beam path is confined to significantly limit the degree of accessibility of the open beam, a hazard analysis shall be effected by the LSO to establish the NHZ.

 Enclosed Beam Path

When the protective housing requirements are temporarily relaxed, such as during service, the LSO shall establish the appropriate controls. These may include a temporary area control and administrative and procedural controls . 

Remote Interlock Connectors

The remote interlock connector reduces the accessible radiation below the MPE on entry to the area protected.

 Beam Stop or Attenuators

The beam stop or attenuator is a device capable of preventing access to laser radiation in excess of the appropriate MPE level when the laser or laser system output is not required.  

Laser Activation Warning Systems

An alarm, a warning light or a verbal "countdown" command used during activation or start-up of the laser.

 Emission Delay

Emission delay provides sufficient time prior to emission of laser radiation to allow appropriate action to be taken to avoid exposure to the laser radiation. 

Remote Firing and Monitoring

Remote firing and monitoring console allows the laser to be operated from a remote location, removing the operator from the hazard.

Equipment Labels

All lasers (except Class 1) shall have appropriate warning labels affixed to a conspicuous place on the laser housing or control panel.

Area Posting Signs

An area which contains a Class 3b or Class 4 laser or laser system shall be posted with the appropriate sign. A notice sign shall be posted outside a temporary laser controlled area. Only signs provided or approved by the Safety Office will be posted.