The hierarchy of control for selecting appropriate control measures for laser safety is:
- Engineering controls
- Administrative controls
- Personal protective equipment
Even then there is a hierarchy within each type of control and in practical terms, laser safety will be a combination of some or all elements depending on the risk or class of laser.
Where an assessment identifies a specific risk with the laser system, then a ‘hierarchy of control’ must be followed. For non-beam hazards these are outlined within individual University policy statements. For beam hazards, the starting point for all lasers is ‘fully enclosed with fixed guarding’.
If a risk assessment identifies that it is not practical to fully enclose the laser at all times, then it must be justified within the assessment and a suitable combination of engineering, administrative and personal protective controls identified to manage the risk. The use of personal protective equipment must always be the last option and, if necessary, there must be clear administrative controls to ensure it is correctly applied.
British standard PD IEC TR 60825−14: 2022 outlines a basic approach to laser safety for the different class of lasers. This can be summarised as:
Class 1
Class 1 laser products/systems do not require any special precautions or formal control measures. The exception is where a product consists of a totally enclosed Class 3R,3B or 4 laser system and access is required for the purpose of servicing or alignment. In this case, it should be included on the laser inventory and there should be local rules developed for that activity.
Class 1M and 2M
Class 1M and 2M products can be hazardous if the output is viewed with optical instruments. Modification of these products needs to be carefully assessed, reclassification may be necessary and the appropriate control measures detailed.
Class 2
For Class 2 laser products, protection is based on exposure being limited by the natural aversion response (0.25 sec). Simple measures such as information to users not to deliberately aim the beam at people or stare into the beam, as well as the need to terminate the beam at the end of its useful path will be sufficient.
Class 3R
For Class 3R products, the control measures will include:
- terminating the beam at the end of its useful path
- avoiding beam paths at eye level and where practicable enclose the beam
- instruction and training to an appropriate level
- taking care to prevent unintentional specular reflections
- where non-visible wavelengths are used, an emission indicator device is to be used to indicate the laser is energised
Class 3B and 4
By default, the beam from Class 3B and 4 should be enclosed. Open beam work should be the exception and must be supported by documenting the justification within the risk assessment.
For Class 3B or 4 lasers, each laser laboratory or experiment, as appropriate, should have its own documented local rules based upon the conclusions of a risk assessment.
The name of the departmental laser supervisor and the permitted authorised users, the extent of any laser controlled area and reference to specific protocols that are to be used should be included in the local rules.
All the above control measures indicated for Class 3R lasers should be used as well as safety interlocks (where a risk assessment justifies this), key control, beam stop/shutter and the full list of user precautions outlined in the British Standard. Laser controlled areas need to be defined and warning signs used.
The local rules should be displayed in a prominent position, ideally on the entrance door to the laser controlled area.