The proliferation of lasers in industrial processing brings a number of benefits to companies, but also entails specific risks associated with the emission of hazardous laser radiation – both direct and diffuse. In order to effectively prevent them, it is necessary to have a thorough knowledge of safety regulations regarding protection from artificial optical radiation and to implement them consistently.
Its consequences can vary – depending on the wavelength, mode and output power of the laser, the nature of the radiation (direct/diffuse), exposure time, and the irradiated organ.
Effects of eye and skin exposure to laser radiation
| Radiation range | Eye | Skin |
|---|---|---|
| 180-400 nm | photochemical and thermal damage to the cornea and lens | erythema |
| 400-700 nm | photochemical and thermal damage to the retina | uszkodzenia termiczne |
| 700-1400 nm | thermal damage to the cornea, retina and lens | thermal injuries |
| 1400-2600 nm | thermal damage to the cornea, retina and lens | thermal injuries |
| 2600 nm-1 μm | thermal damage to the cornea, retina and lens | thermal injuries |
The human organ most vulnerable to damage is the eyes – both because of their sensitivity to radiation and because of the properties of the laser beam, which in the infrared and ultraviolet range is completely invisible to the eye, and thus contact with it does not stimulate the body’s defense response (eyelid closure). The degree of damage to the eye depends on the intensity of the radiation and where it falls: radiation in the 400-1400 nm range falling on the central fovea of the retina can cause permanent damage to the retina, and thus blindness. For the skin, on the other hand, short, high-powered pulses wreak the most havoc, the impact of which can lead to tissue charring.
Effects of laser radiation on the eyeball
As statistics show, this danger is not at all abstract. CIOP data show that of all accidents when operating laser equipment, nearly half (44%) involve exposure to laser radiation. Its cause was both the lack of appropriate protective equipment (goggles and safety goggles) and the poor selection or defectiveness of such equipment, as well as accidental contact resulting from the lack of regulations limiting third-party access to the laser workstation. Hence the importance of both knowing the class of laser and the rules of use and safety rules for working with laser equipment.
| Classes of lasers and laser devices (according to PN-EN 60825-1:2014:11) | ||
|---|---|---|
| 1 | Laser radiation completely safe in all conditions | |
| 1M | Emission of radiation in the region of λ = 302.5 ÷ 4000 nm, safe provided that optical elements (such as lenses) are not used | |
| 2 | Emission of radiation in the area of λ = 400 ÷ 700 nm, safe provided there is no direct exposure to the eye | |
| 2M | Radiation emission in the region of λ = 400 ÷ 700 nm, safe as long as there is no direct exposure to the eye and optical elements are not used | |
| 2M | Radiation emission in the region of λ = 302.5 ÷ 106 nm, safety glasses required | |
| 3B | Lasers absolutely dangerous with direct exposure to the eye and sometimes to the skin, safe to look at diffuse radiation | |
| 4 | Radiation emission hazardous to eyes and skin under all conditions, can cause fire or explosion | |
It is the laser manufacturer’s responsibility to mark the class of laser and to provide operating instructions that take into account the appropriate selection of protective equipment. However, the precautions taken by the company’s management play an equally important role.
The first step in this case should be the preparation of a detailed risk assessment that takes into account the basic parameters of the laser device, as well as all types of hazards posed by the laser. After all, in addition to radiation exposure, it can generate electrical, vapor and gas, fire and explosion hazards, as well as those associated with associated radiation (non-laser, such as X-rays). The guide “Artificial Optical Radiation – Principles of Occupational Risk Assessment,” available from the Central Institute for Labor Protection, can help in making a proper assessment.
The basic guidelines and recommendations for laser users in the table below may be of additional help.
Basic requirements and recommendations for users of laser equipment by laser class
| Requirements and recommendations | 1 do 2M | 3R | 3B | 4 |
|---|---|---|---|---|
| Appointment of laser safety inspector | • | • | • | |
| Use of remote locking switch | • | • | ||
| Key startup | • | • | ||
| Use of a laser beam limiter or attenuator | • | • | ||
| Radiation emission signaling device | • | • | • | |
| Use of warning signs | • | • | • | |
| Shielding of laser beams | • | • | • | |
| Avoiding mirrored reflections | • | • | • | |
| Use of personal eye protection equipment | • | • | ||
| Use of protective clothing | • | • | ||
| Safety training for workers on working with lasers | • | • | • |
A properly prepared risk assessment should take into account three basic aspects: the hazards caused by the laser system, its working environment and the level of staff awareness. Similarly, the leveling of the risks identified in this process should include both the individual protection measures (the laser system) and the collective protection measures applied in the room where the laser works (the working environment), as well as training for personnel to increase awareness of the risks associated with laser radiation.
