The user guidance (Section 3) of EN 60825-1 'Safety of laser products Part 1: Equipment classification, requirements and user guide' was drafted in 1974 and has remained largely unaltered since. Pro Laser is collaborating in a BSI-funded initiative to update the guidance, in particular to step beyond the constraints of listing precautions based on hazard classification alone, to making the user guidance consistent with the modern risk assessment approach.

A hazard is defined as something with a potential to injure and laser radiation is one such hazard. At the heart of laser safety standards is a hazard classification scheme which ranks the hazard according to whether or not the MPE can be exceeded under any of several defined circumstances (e.g. direct accidental viewing with an optical instrument sets the limit for visible Class 3A). The classification scheme is broadly analogous to the term 'degree of hazard' which is sometimes used in general safety to denote the severity of injury that a hazard can inflict.

Laser safety guidance based only on the laser hazard classification scheme often provides too crude an approach to selecting appropriate safety control measures. Product and workplace directives are, however, based on risk assessment; that is to say, risk assessment is the legally mandated approach to safety.

There are hazards involved in all activities and whenever there is a possibility of exposure to a hazard then there is also a risk of injury, but it is rarely necessary or even possible to completely remove the risk. What is required by the various product and workplace safety directives is to reduce the risk during use (and also under reasonably foreseeable conditions of failure and misuse) to a tolerable level. This 'tolerable' level will vary widely depending upon the application and circumstances of use, and setting the level is a matter of judgement. Best practice is the best indicator in the absence of judicial pronouncements on the subject. In practice, risk assessment can provide a better and more flexible approach to finding the optimum mix of control measures. So what is 'risk' and how is it assessed?

Risk and risk assessment

Risk is an attribute associated with an activity. It is a property of the activity that combines the likelihood of exposure to the hazard with the severity of the resulting injury. For example, frequent exposure to a hazard with a potential to cause a minor injury might be ranked equal in risk to that of an activity where exposure to a hazard with a potential to cause a more serious injury was less likely.

The reduction of risk to tolerable levels is an iterative process. There is no standard procedure or style of documentation for this process. Nevertheless, the stages involved are universal:

1. Identifying the potentially injurious situations;
2. Assessing risk for potentially injurious situations;
3. Selecting controls and repeating the process.

It is usually difficult or impossible to quantify the two elements that make up the risk. At Pro Laser, for example, we place the likelihood of injury into one of five categories (ranging from likely to improbable), taking account of the frequency of exposure to the hazard, the time of exposure to the hazard and the probability that, when exposed, the hazard will not be avoided. Similarly, we place the severity of injury into one of four categories from fatal to no injury and add a fifth category for damage to plant or environment.

Applying the process to lasers

The most important step of a risk assessment is to make a list of potentially injurious situations that could arise in the use of the laser equipment, including those of installation, normal operation, maintenance and service. The list of 'what could go wrong' might be derived by considering activities systematically, for example, or randomly by 'brainstorming' and then prioritising. There are three key types of issue which the user should focus upon when drawing up the list of potentially injurious situations:

1. the hazards not already isolated by existing controls,
2. control of access to the laser area and the operations within it, and
3. the personnel at risk and their level of awareness, protection and training.

Simply to know by how much an exposure exceeds the appropriate MPE is not always sufficient to estimate whether a laser injury will be major or minor, but there is little other relevant data available. The important considerations will include eyes or skin, retinal or corneal (for ocular injuries), large or small area exposure (for skin burns), duration of laser radiation exposure.

For situations where the risk is assessed to be above a tolerable limit, control measures have to be considered. Engineering controls should be given primary consideration, with personal protective equipment the last resort. The assessment process is then repeated, until all the risks are assessed to be tolerable.

Risk assessment provides a 'level playing field' whereby laser hazards can be dealt with in the same way as electrical, mechanical and other hazards. It provides a degree of flexibility in the design and installation of control measures that the simple hazard classification scheme does not and it challenges laser standards writers and some safety consultants to stop treating lasers as 'special cases'.

Pro Laser offers considerable experience in conducting in-house risk assessments. We provide comprehensive documentation summarising the risk from laser radiation and associated hazards