Laser risk assessment

The Control of Artificial Optical Radiation at Work Regulations require a ‘suitable and sufficient’ assessment of risk if work is carried out that creates a reasonably foreseeable risk of adverse health effects to the eyes or skin. As a general rule, any work involving open beam Class 3R, 3B, or 4 lasers can be considered a reasonably foreseeable risk. The same is true for lower class lasers where specific activities introduce new hazards (e.g. refocusing a Class 2M laser via a microscope objective or overriding the interlocked contacts on a Class 1C product).

Make sure there is a documented risk assessment for:

• any class 3R, 3B, or 4 laser
• any manipulation of a lower class laser that might increase the risk under certain operating conditions (e.g. use of magnifying instruments)
• any lower class laser whose non-beam hazards pose a significant risk, even though the risk from the beam itself is negligible
• embedded ‘Class 1 by design’ products encompassing Class 3R, 3B, or 4 lasers if the beams might be exposed during routine and frequent (i.e. daily, weekly, or monthly) service and maintenance

The purpose of a risk assessment is to systematically identify all hazards (both beam and non-beam) associated with the laser system and assess the risk arising from both normal and/or non-routine use. The risk assessment must identify appropriate ‘engineering controls’, ‘administrative controls’ and, if risks still then exist, ‘personal protective equipment’.

It must be completed prior to the installation or first use of the laser and must include ‘beam’ and ‘non-beam’ hazards. As with other types of risk assessment, the significant findings must be documented. The Laser Registration Form (LS-1) and Laser Risk Assessment Form (LS-2) can be used for this purpose.

Make sure your laser risks assessments have considered and assessed:

• the irradiance or radiant exposure, wavelength, duration of exposure
• the maximum permissible exposure limit (MPE) and nominal ocular hazard distance (NOHD)
• the likelihood and effects of exposure on those who might be affected (e.g. staff, students, visitors, support staff, service engineers, and emergency services)
• the effects of exposure on those individuals who might be at particular risk (e.g. visually impaired, photosensitised)
• any indirect effects on individuals, such as glare, distraction, fire, explosion
• availability of alternative equipment designed to reduce the level of exposure (e.g. lower powered lasers, enclosures, remote viewing aids)
• multiple sources of exposure, both in a single system or within a single area (e.g. multiple laser tables in one laser controlled area)

Undertake a regular review of the risk assessment at least annually, or following any significant change in the setup or operation of a laser product or system.

Ensure those completing a laser risk assessment are competent to do so or, if necessary, consult the department laser supervisor for advice and assistance.

So that an appropriate assessment is conducted, you should ensure that you have competent risk assessors with sufficient knowledge and experience of the laser itself and an understanding of the laser risk assessment process. Depending on the complexity of the system and the class of lasers involved, it may be necessary to involve a small team of assessors, such as the supervisor, individual users and departmental laser supervisor. It may also require knowledge of laser calculations or measurements which, depending on the level of information required, could indicate the need for further training or involve the University Laser Safety Officer, specialist users or external contractors.

Clearly define and document the process, activity, or laser product that is under assessment.

The first part of completing a ‘suitable and sufficient’ assessment is to define the process, activity or product. For example, will the risk assessment cover the use of a single laser or a group of lasers in a specific area? The more detail you put into defining what is being assessed, the easier it is to identify possible hazards and associated risks. The information required in this section is principally the same as that recorded during registration. The Laser Registration Form (LS-1) can be used for this purpose, with consideration to:

• define the room, location, and expected use of the laser
• sketch the installation, from where it is positioned within a room to the planned beam path
• detail the laser components involved. Contact the manufacturers to obtain beam specifications of all the lasers in the system. Consider what supporting equipment is needed to operate the laser, such as electrical supplies and cooling units
• outline how the lasers interact with each other and how the beams are going to be delivered from the laser to the point of use. For instance, are optical fibres/flight tubes used or will the beam be delivered via optical components? Will the beam specification be modified in any way, such as the use of filters or beam splitters? How is this modification controlled, either manually or through computer-controlled systems? Are there sources of unexpected beam paths, such as reflective components or surrounding materials?
• outline the actual laser process, such as spectroscopy, material processing, or medical treatment. What other items are involved in this process, such as chemicals, biological agents, materials?
• describe the environment, such as the access to and general use of the room, the size, lighting, temperature, and ventilation
• identify the types/groups of people who might be affected by the use of the laser

As well as the routine use of the laser, there will be risks associated with installation, maintenance, adjustment, movement and disposal. Therefore, consider the life of the laser rather than just the experiment itself to identify whether the risk varies.

Identify both the beam and non-beam hazards associated with the process, activity, or laser product that is under assessment.

Having defined the system, it should be relatively easy to identify the significant hazards (i.e. sources of potential damage, harm, or adverse condition). However, the risk associated with certain hazards will vary according to where in the system it is being used. For instance, the risk from a Class 4 beam inside an enclosed laser product is significantly less (due to the enclosure around the beam), than when the beam is delivered to another instrument on an open bench. 

It is advisable to break down the process into sections and the hazards in each section identified and assessed independently. This also helps in reviewing the assessment when modifications to the system are made, for the risks may rarely change with the laser itself but might significantly differ in how the beam is delivered. The following outlines examples of hazards that might be considered:

1. Laser

This section covers all aspects of the laser itself from the power supply to the aperture at the front of the laser equipment. 

The principle concern will be the beam hazards. These can be summarised as:

However, to fully understand the hazards it will be necessary to consider the laser specifications and how, if any, the exposure to the laser beam itself might occur.  For instance, is the beam always fully enclosed or is there a need to remove guards (e.g. during alignment or servicing). If exposed:

• What class of laser is involved? 
• Can a lower class be used instead or the output power restricted?
• What frequency (or range of frequencies) does it operate at and therefore what type of harm is possible (i.e. skin, eye harm and fire/explosion)?
• Is the beam visible or, if not, how is the beam to be detected?
• Is the beam continuous or pulsed? 
• What is the maximum permissible exposure (MPE) limit for the laser? The University has access to the LaserBee software that can be used to determine MPE levels. Could the laser output (e.g. accessible emission limit) exceed the MPE? If so, this could constitute a significant risk
• If there is any uncertainty over the potential risk, what is the nominal ocular hazard distance (NOHD)? The NOHD is the ‘safe’ distance away from the laser aperture where the level of exposure (i.e. irradiance or radiant exposure) is less that the MPE. If, for example, the NOHD is greater than the dimensions of the room, there will clearly be a risk of eye injury.  However, it the beam specifications mean the NOHD is restricted to a zone inside the room, then a decision needs to be made as to whether the control measures will change if an individual is stained inside or outside of that zone
• Those completing a laser risk assessment should know how the laser emission relates to both the MPE and NOHD.   

In addition to the beam hazards, are there non-beam hazards, such as:

• electrical
• cooling systems
• compressed or cryogenic gases
• cooling systems
• hazardous substances or chemicals
• manual handling
• noise
• other non-ionising or ionising radiation (e.g. x-rays)
• trip hazards

2. Beam delivery

This section covers the delivery of the laser beam from the laser equipment to the point at which it is used. It includes both intentional beam paths, such as the use of mirrors, and unintentional beam paths, such as reflectance from surfaces should the beam become misaligned. For instance:

• Will the beam be open or closed at any point? 
• Will this differ during alignment or servicing?
• What type of optics are involved? 
• Are the optical components coated to reduce reflections?
• Are the optics fixed and secured or is the beam delivered by a roaming device, e.g. hand-held fibre optics in medical equipment?
• Are there any beam splitters or filters? Can these be modified either manually or by computer control? If computer controlled, could this produce unexpected beam parameters?
• Are there any reflective surfaces and if so, will this cause spectral or diffuse reflections?

3. Laser process

This section covers the hazards that might arise from the intended use of the laser beam, such as:

• material processing
• medical treatment
• microscopy
• spectroscopy

4. Environment

This section covers the prospect that the risks associated with a laser and its operation may differ depending on the location and the potential exposure to different people. For instance:

• dust
• humidity
• lighting
• temperature

Identify everyone at risk of exposure associated with the process, activity, or laser product that is under assessment.

This stage of the risk assessment should enable you to identify everyone at risk of exposure and the way any exposure to the hazard is likely to occur. Those at risk of exposure may include:

• academics
• postdoctoral research assistants
• visiting researchers
• support staff
• technicians
• postgraduate students
• undergraduate students
• others in the department
• contractors
• laser maintenance engineers
• security staff
• cleaners
• members of the public
• others

Having identified all those who might be exposed to laser risks, you should consider how any exposure could occur. Look at each identified hazard and judge how people might be exposed to it. For example, a stray laser beam reflected up from the optical bench could be caused by loose or failed optics, reflective equipment, jewellery, poor alignment procedures etc. The beam could strike other people working in the room, someone entering the room, and potentially someone outside the room through unprotected windows.

When assessing how people could be harmed, do not just consider your own experiment. Think about the entire environment. What access is there to the room? Is there more than one entrance? How many experiments are there? How cluttered is the room? Are different wavelengths used in the same room? Will anyone need to operate the laser alone? What can go wrong and what would happen if it did? Identify the reasonably foreseeable accidents.

If you have already determined the nominal ocular hazard distance (NOHD), you can assume that any exposure within that distance will be significant. The remainder of the risk assessment can simply address the adequacy of current controls to prevent exposure and what more can reasonably be done to prevent exposure. Possible exposures beyond the ocular hazard distance may not have potential to cause physical eye damage but should be prevented so far as reasonably practicable, particularly if there is still a risk from 'flash blindness' or distraction.

The University does not require laser users to undergo routine ophthalmic examination, but departments must ensure that laser users who believe themselves to suffer from significant pathological conditions of the eye consult the University Occupational Health Service prior to commencing laser use. The user declaration in the Laser User Authorisation/Training Record (LS-4) can be used to highlight the importance of this issue to the laser user.

Identify the existing controls measures already in place and assess whether these are sufficient to control the risk of exposure associated with the process, activity, or laser product that is under assessment.

This stage identifies all engineering and administrative controls that are currently in place (or proposed if this is a risk assessment of a planned experiment). These should be outlined and the resulting risk should be considered with these in place. If the risk is controlled, no further action is required. However, if any significant risk remains, additional controls must be identified and implemented. For instance, is it reasonable to replace an existing procedural control, such as manually locking a door, with a preferable engineering solution, such as installing interlocks?

As a minimum, the prescriptive requirements of the relevant British Standards must be addressed, such as those given in BS EN 207 & 208 for laser eye protection. Ultimately, a ‘hierarchy of control’ must be considered, i.e. full enclosure, temporary or partial enclosure, administrative controls, personal protective equipment and/or a combination. In identifying suitable controls it may help to consult the departmental laser supervisor, University Laser Safety Officer, other departmental laser users or even other University laser users. The suitable solution should be recorded.  

Where significant risks exist which cannot be engineered out, any necessary administrative controls should be documented in the form of laser local rules. The risk assessment drives the degree of detail required in the local rules, so if the risks are still high after engineering controls are applied, the degree of detail required in the local rules will be significant. 

Outline any additional control measures required and ensure they are implemented.

Where actions are identified to address significant risks, there should be a system in place to ensure completion. Individuals or groups should be assigned actions along with a proposed timescale. Once these are completed, the adequacy of the control should be assessed and, if appropriate, the document signed off. Periodically, following a significant change, or following an incident, the assessment will need to be reviewed to see if any additional controls are required.