FEATURE
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Stay safe from lasers

William Payne investigates safety standards within the photonics industry

A decade ago, lasers were mostly restricted to laboratories, industrial workplaces and hospitals. They were controlled and used by professionals. Today, the fastest growth in lasers is in unregulated beauty salons, where they are used for beauty treatment and hair removal. The second fastest-growing area is in DIY and unregulated personal use.

In just a decade, lasers have gone from being mainframes to iPods. The increasing ubiquity of lasers throughout the workplace, and the growing range of uses that they are now being put to, is creating real challenges for managing their safety.

Lasers can result in injuries ranging from mild to severe burns, to blindness and death. Very short, high-powered laser bursts can cause severe trauma and plasma damage to tissue, even if the burst is too short to cause burns. Longer laser bursts can cause burning. At temperatures of just 55oC, serious damage to tissue can begin to occur. Above 100oC, vaporisation begins to take place, and at 300oC, the flesh chars. Lasers can also cause severe photo-chemical reactions. The retina is particularly sensitive to blue light, with photo-chemical damage occurring even without any significant rise in temperature.

To guard against these dangers, a range of products are marketed. These include protective goggles, encapsulation of laser systems, interlocks that can shut off a laser, and laser beam shutters that can block the beam. Ancillary devices include visible pilot beams that clearly mark out the path of high-powered beams. Leading vendors include Laservision, Lasermet, Elliot Scientific and Laser Physics.

Key European laser safety standards include the main laser safety standard, EN 60825, which lays out the safety classes of lasers and requirements for working safely within each class. Other standards include EN 207 and EN 208, which focus on protective devices such as eyewear. However, increasingly, the main approach to laser safety is the workplace safety assessment and staff education.

‘There’s been a real shift in recent years in how we approach laser safety,’ says Roy Henderson, author of Laser Safety (Institute of Physics Publishing, 2003) and founder of Bioptica. ‘The laser classification system – how dangerous a laser is – has become just one component in how we do safety. The requirement to do a risk assessment means that laser safety is now equally focused on what the laser is being used for, the workplace environment and other variables. That means we are now looking at the real risk involved, not just at the class of laser.’

New European Directive

In February this year, the European Parliament passed new legislation tightening up safety standards in any environment using laser or infrared devices. The Health and Safety Directive – Optical Radiation sets new limits for permissible levels and duration of laser exposure, and places new requirements on employers to carry out risk assessments and ensure that workplace design and layout complies with European safety laws. The new directive also lays down minimum standards for prevention and early diagnosis of potential damage to eyes and skin from industrial light sources.

The directive is designed to extend European laser safety legislation to the increasing use of lasers in the construction industries and shops, as well as growing use of laser devices in the field. As a directive, its implementation will depend on how each member country decides to interpret the legislation’s requirements.

Laser safety attitudes

Given the well-attested dangers surrounding lasers, and the general fear of them among non-users, it is surprising that workplace use often becomes lax. Laser safety practitioners have to confront working attitudes to lasers among staff and management just as much as the design and layout of the workplace. Chief among these are complacency and commercial pressures. Lack of access to proper laser safety gear, accompanied by time pressures, can compromise laser safety.

So can pressures to reduce costs: some retailers are now providing barcode scanning points for shoppers to scan through their own shopping in a bid to increase turnover. A national newspaper recently described young children climbing onto these scanning units while their harassed parents wrestled with their shopping. Although alarms repeatedly went off, these were ignored by busy staff.

Unhelpful rules and regulations are another contributor to lax laser safety. Regulations that are primarily designed to provide legal cover in the case of an incident tend to be incomprehensible to staff and, consequently, are often ignored. Surveys have shown that it is younger and more junior staff who are at greatest risk from laser incidents.

Maximum permissible exposures

A key concept in determining the safety of a laser device is the Maximum Permissible Exposure, or MPE, level. Controversy over MPEs extends over the whole field of radiological protection, not just laser safety. Dr David Sliney of the US Army’s Laser Branch has questioned currently accepted threshold levels for laser safety, as well as MPE levels. He has argued that injuries can be shown occurring below the generally accepted safety threshold levels. He has also questioned the models used to calculate safety levels, arguing that small variations in any number of different factors can produce substantial changes in the actual threshold of laser safety.

It’s not just light

Although most attention with laser safety focuses on the risk of light to the skin and, especially, the eyes, lasers pose other hazards as well, chief among these is the danger of electrocution. Some laser safety specialists argue that, in practice, these non-light hazards pose greater dangers to users than direct laser radiation – especially electrocution. A survey of 60 laser incidents found that the most serious effects – four deaths – all resulted from electrocution.

Other dangers arise from hazardous chemicals, exploding tubes, fire, airborne particulates and secondary radiation, such as UV or x-rays.

Trends in laser safety

Dr Mike Green, principal laser safety consultant at Pro Laser, sees portability of laser devices emerging as a major challenge to established safety approaches: ‘In labs today, laser devices are so portable, and with their own battery power supplies, that these can create real safety issues. A decade ago, labs might have one, stationary laser device powered from the wall. It was

possible to create comprehensive safety approaches, including power interlocks. Now, with labs having tens of smaller portable devices, moving from lab to lab on demand, it becomes very difficult to establish comprehensive safety. In particular, since they are battery powered, setting up door interlock systems becomes much more difficult in practice.’

Bioptica’s Henderson sees the shift from large, stationary lasers to smaller, portable devices in many workplaces, including laboratories, as changing the nature of laser safety from prescription to greater workplace independence: ‘We have had to move on. The old approach that focused on laser classes was based on the assumption that lasers were large, heavy objects that were only found in labs and used by professionals. Now we have lightweight devices that can be used anywhere. The risk now is associated not so much with laser class, but rather purpose of use. The onus is now far more on workplaces being equipped to make their own judgment.’

By contrast, Green sees the increasing use of control systems in manufacturing applications as reducing the safety burden on workforces in the industrial workplace: ‘We are definitely seeing that industrial lasers are now much better designed, and far safer as a result. The rise of good manufacturing practice and the spread of SCADA technologies has contributed to greater laser safety in industrial manufacturing. Control systems now take a lot of the pressures away from industrial users.’

Future challenges

Henderson sees the spread of lasers out of established areas, into the hands of untrained consumers as a growing challenge: ‘As lasers have become lightweight, portable and cheaper, we’re finding that they’re being bought for other purposes. People are buying them because they might be doing a bit of club DJ-ing on the side. Lasers are also being incorporated into more and more DIY products. Users in these uncontrolled environments are frequently dismissive of safety warnings and don’t understand the dangers involved.’

However, Henderson believes that the biggest challenge in laser safety is the growing use of lasers in unregulated health and beauty clinics, where powerful lasers are being used by untrained staff: ‘Lasers are widely used across hospitals and private clinics. Now they’re moving increasingly into beauty salons, where they’re being used for beauty and hair removal purposes. This is now the biggest growth area in laser products, and it’s an environment that is much more difficult to police. We’re seeing many staff without adequate training using these devices. The Healthcare Commission is putting a lot of effort into attempting to bring these clinics and salons into a regulated system.’

For Green, one of the big challenges for future laser safety is the increasingly high powers available from fibre lasers: ‘Fibre lasers open up the opportunity to have multiple laser workstations all fed from one very high-powered laser engine. Having kilometres of fibre cable carrying a high-powered laser source is going to introduce all sorts of challenges for laser safety in future industrial workplaces. The technology here is currently developing faster than the safety devices. We can guard against over-heating in the cable, but a laser shut-down in the case of a cut cable is not going to be instantaneous. Robotic tools using lasers also create their own challenges.’

‘On the research side,’ says Green, ‘the biggest challenge is the increasing use of short pulse lasers and the growing availability of tunable multiple wavelengths in the same laboratory area. It becomes almost impossible to get eyewear that will protect against all the different wavelengths that a tunable laser can produce.’

Henderson believes a way forward is to build greater safety into laser devices: ‘There’s a lot of scope for building greater safety into devices. EN 60825-1 is the main laser standard, but it does very little to push manufacturers to make their products safer. What it requires is a hazard assessment, and then manufacturers to label and signpost their products accordingly. There is real scope for engineering in greater safety into lasers, and that would remove quite a bit of the onus from users to adopt safe procedures.’