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Information Sheets
Safety
Laser Safety
A LASER generates a high intensity beam of light. This laser radiation can be visible or invisible with wavelengths ranging from 180nm to 1 mm. The intensity is often sufficiently high that exposure to laser radiation can be severely hazardous. Thus the hazards associated with laser radiation require to be well known and the appropriate protective measures taken.
The risks associated with laser system hazards fall into six main categories:
- Exposure to Laser radiation causing eye damage
- Exposure to laser radiation causing skin damage
- Electrical shock
- Exposure to fume
- Exposure to chemical hazards
- Other risks
The EN and IEC 60825 series of standard and technical reports covers the safety aspects of laser products, forming the basis both of manufacturer’s requirements for conformity to product legislation and, for European countries that have no National laser user standards, the best practice guide for safe laser use.
The IEC Series consists of the following parts:
Part 1 – Equipment classification, requirements and users guide (the User’s guide is replaced by Part 14. A brief description of the classification structure is shown below)
Part 2 – Safety of optical fibre communications systems
Part 3 – Guidance for laser displays and shows
Part 4 – Laser guards
Part 5 – Manufacturer’s checklist for IEC 60825-1
Part 6 – Safety of products emitting optical sources, exclusively used for visible information transmission to the human eye
Part 7 – Safety of products emitting infrared optical radiation, exclusively used for wireless ‘free air’ data transmission and surveillance
Part 8 – Guidelines for the safe use of medical lasers
Part 9 – Compilation of maximum permissible exposure to incoherent optical radiation
Part 10 – Application guidelines and explanatory notes about IEC 60825-1
Part 12 – Safety of free space optical communication systems used for transmission of information (to be published)
Part 13 – Measurements for classification of laser products (to be published)
Part 14 – A User’s guide
Risk of eye injury
Eye damage is often regarded as the main risk from laser radiation exposure. This notion arises from the fact that a visible and near-visible (near-infrared) laser beam can be focussed by the eye to a small spot on the retina (the light sensing area at the back of the eye) with a resultant high intensity. This may cause damage to occur on the retina, which can cause total or partial loss of vision. Since the retina does not register pain, injury may only become apparent later. All retinal damage should be regarded as permanent.
Only visible and near infrared radiation is a retinal hazard; the output of lasers operating at ultraviolet or mid and far-infrared wavelengths is fully absorbed by the cornea, aqueous and lens (i.e. the anterior) of the eye. In this case, excess exposure can cause burns on the cornea and lens, possibly resulting in a corneal scar or lens opacity (cataract).
Risk of skin injury
High power laser radiation will damage the skin. Indeed this effect is intentionally utilised in certain medical procedures. Hans and face are commonly affected. Depending on the severity of exposure, this can lead to:
- Reddening (erythema)
- Burns
- Skin aging
- Increased pigmentation and pigment darkening
- Increased sensitivity to sunlight
Exposure to some laser radiation (especially ultraviolet) may contribute to certain types of skin cancer.
Risk of electrical shock
Power supplies for most lasers use high voltages, often with stored energy. Whereas most hazards can incapacitate, electrical shock hazards can kill.
All laser power supplies should be regarded as potentially lethal and protective housings should not be removed or displaced except by trained and authorised personnel.
Risk from fume
Industrial lasers are used for material processing – typically welding, drilling and cutting. These processes often involve the removal of material and invariably result in the generation of vapour, fume and fine airborne particulate (i.e. fume).
The use of medical lasers often produces bio-hazardous by-products. Such by-products should always be regarded as potentially harmful and effective steps must be taken to eliminate or minimise inhalation.
Risk from Chemical Hazards
Materials used in certain types of laser may themselves give rise to a chemical hazard if not properly handles or contained. Examples of laser in this category are dye lasers and Excimer lasers.
In a dye laser, the active medium comprises of an organic dye dissolved in an organic solvent. Both dyes and solvents should be regarded as toxic and in some cases carcinogenic.
Excimer lasers typically use toxic gases such as hydrogen chloride and fluorine, along with less toxic gases such as neon and helium. Extreme care is needed in handling the more toxic gases. Care is also needed when charging equipment such as gas scrubbers, which contain caustic materials.
Other Risks
Additional risks may be present, according to the type of laser system. The additional hazards include:
Risks from noise hazards
Large laser systems can generate noise at levels above legislated limits. The noise may be generated by the laser system itself or the associated process.
Risks from ionising radiation
Some high power gas laser systems incorporate devices which are capable of producing X-rays. This is especially the case when voltages used exceed 15 kV.
Risks from explosion
The following items have a potential for explosion:
- Energy storage capacitors
- Gases
Care must be exercised in evaluating potential explosive or shatter effects of optical components, laser targets and materials being processed.
Risks from fire
High power lasers have a potential for igniting combustible materials.
Particular care is required when processing certain types of materials when oxygen is used as an assist gas. Care is also required with reactive metals such as titanium, zircalloy and magnesium which are easily ignited in the presence of oxygen.
The laser classification system
Below is a brief overview of the laser classification scheme of EN and IEC 60825-1:2007
Class 1:
No risk to eyes or skin
Class 1 laser products are defined as safe in normal operations under reasonably foreseeable conditions, including direct viewing of the laser beam with optics that could concentrate the laser output into the eye. In addition to some intrinsically low power lasers and laser products, Class 1 laser products also include embedded products that totally enclose a higher Class of laser e.g. CD players, laser printers and most industrial laser processing machines.
Class IM:
Low risk to eyes. No risk to skin
Class 1M laser products are defined as safe in normal operations under reasonably foreseeable conditions, including direct viewing of the laser beam, but only provided the user does not employ optics that could concentrate the laser output into the eye. Unsafe conditions include use of a telescope or binoculars with a 1M laser emitting a well collimated laser beam or use of an eye loupe or magnifier with a high divergence 1M source.
Class 2:
Low risk to eyes. No risk to skin
Class 2 laser products are defined as those emitting visible light for which the natural aversion response to bright light (including the blink reflex) prevents retinal injury, including direct viewing of the laser beam with optics that could concentrate the laser output into the eye. These lasers do, however, present a dazzle hazard.
Class 2M:
Low risk to eyes. No risk to skin
Class 2M laser products are defined as those emitting visible light for which the natural aversion response to bright light (including the blink reflex) prevents retinal injury for direct viewing of the laser beam but, as with Class 1M laser products, only provided the user does not employ optics that could concentrate the laser output into the eye.
Class 3R:
Low risk to eyes. Low risk to skin
Class 3R laser products are defined as those for which the output is up to a factor of five over the maximum allowed for Class 1 or Class 2. Because of safety factors built into the limits for these classes, the risk of injury for direct viewing of a Class 3R laser beam remains low, but greater efforts should be taken in the use of these lasers to prevent direct eye exposure, especially for invisible Class 3R lasers.
Class 3B:
Medium risk to eyes. Low risk to skin
Class 3B laser products are defined as those for which direct exposure of the eye is hazardous, even taking aversion responses into account, but scattered laser light is usually safe. The higher power Class 3B lasers are also a skin hazard, but the natural aversion response to localised heating generally prevents a skin burn.
Class 4:
High risk to eyes and skin
Class 4 laser products are defined as those for which direct exposure of the eye and skin is hazardous and scattered laser light may be hazardous to the eyes. Such lasers are also a fire hazard.