A Guide to Laser and Non-beam Hazards

Laser beam hazards

The light in a laser beam can be hazardous to exposed eyes and the skin. The risk of harm can arise out of direct exposure to the beam or unexpected radiation release due to misalignment of optical components or broken optical fibre.

Depending on the laser’s power output and wavelength it can cause eye and skin tissue can burn (thermal effects), produce damaging chemical reactions (photochemical effects) or physically damage surrounding tissue (acoustic transients).The eye is particularly vulnerable to damage. Injuries can occur at lower power levels than for skin. Cornea damage occur at wavelengths  < 315 nm and retinal damage at wavelengths in the range 400 nm to 1400nm. IR radiation 700 nm  to 1mm can cause cornea burns and flash burns to the eye. The skin can experience reddening (erythema), accelerated skin aging and increased risk of skin cancer. In some cases IR lasers can burn the skin.

Laser Classification and Laser Class description

Lasers in the UK should be classified and labelled accordingly to the British Standard on Laser Safety, BS, EN 60825-1:1994. The laser class reflects the potential harm it presents if the beam is exposed to eyes or skin. Other countries classify lasers slightly differently to the British Standard and may use Roman numerals. If you are unsure about your laser’s class or it has Roman numerals on the label don’t take unnecessary risks. Seek advice from the Departmental Non-Ionising Radiation Protection Advisor (DNIRPA) or the University Non-Ionising Radiation Protection Advisor (UNIRPA).

Class 1

The laser power output is below the level at which it is believed eye damage will occur. Some laser products may contain a higher class laser, but will be a Class 1 Laser Product because under normal operations the higher class laser beam is inaccessible.

Class 1M

The laser beam is more powerful than Class 1. The beam is highly divergent (it spreads out) and only a small amount of the whole laser beam will enter the eye. This class of laser can become dangerous if viewed using a magnifying optical instrument.

Class 2

The laser power output is limited to below 1 milliwatt (mW) and in the visible wavelength range between 400 nm to 700 nm. A person exposed to the beam will be protected from injury by their own natural aversion response (blink reflex).

Class 2M

The laser beam is more powerful than Class 2 and in the visible wavelength range between 400 nm to 700 nm. However, the beam is highly divergent (it spreads out) and only a small proportion of the whole laser beam will enter the eye and that will be below 1 mW. This class of laser can become dangerous if viewed using a magnifying optical instrument.

Class 3R

The laser power output is limited to below 5 mW and the wavelength range is between 180 nm to 1 mm. Exposure to the beam could potentially cause eye injuries.

Class 3B

3B lasers have a maximum 500 mW (half a watt) power output. Hazards arise from direct beam viewing and reflection of the beam. 3B lasers have sufficient power to cause an eye injury.

Class 4

Class 4 lasers have a power output greater than 500mW and there is no upper restriction. They require extreme caution because the direct beam and reflected beam can cause serious eye injury, skin burns and is a fire hazard.

Non-beam hazards

As well as the laser beam hazard, other non-beam hazards are associated with the laser work. Non-beam hazards are grouped into categories. Those most commonly encountered in laser work are:

• Electrical

• Chemical, including fume production

• Mechanical

• Fire

• X-rays and electromagnetic interference

• Other hazards

Electrical Hazards

Potential sources of electrical hazards are high voltage power supplies and laser cavities. For example, a 2kW CO₂ laser typically requires 3 phase supply at 40kW. No electrical work should be carried by unqualified staff. Relevant University Standard: Electrical safety.

Chemical Hazards

Sources of chemical hazards in laser work are laser gases, laser generated fume and particulate matter and cleaning fluids. Relevant University Standard: Working with Hazardous Substances.

Mechanical Hazards

This category covers manual handling of laser equipment and auxiliary equipment, noise , hot work pieces, moving parts in machines and guarding. Relevant University Standards and Guidance: Work Equipment Safety, Buying work equipment: health and safety considerations, and Noise and Vibration. For advice on manual handling risk assessments contact HSAS ex. 2944. For other Health and Safety Standards and guidance follow HSAS A-Z subjects.

Fire

Class 4 lasers present a fire hazard. Direct and diffuse laser beams from Class 4 lasers can combust materials, especially in oxygen rich environments. Relevant University guidance: Fire Safety Information

X-ray and electromagnetic interference

X-rays can be generated by laser power supplies and by laser radiation interacting with a material. Electromagnetic interference is generated for radio frequency excited lasers.

Other hazards

Other hazards, for example lone working, using display screen equipment, working at height, temperature. For other Health and Safety Standards and guidance go to HSAS A-Z subjects.