Protection against laser hazards

For Class 4 lasers, you must apply preventive measures.

Warning

The user is responsible for taking all necessary measures to comply with and enforce safety regulations governing the use of Class 4 lasers. He is also responsible for training the personnel who use the machine.

The user is liable for any failure to comply with safety regulations.

Collective protection measures

The environment in which the laser is used is an important factor in complying with safety measures.

These measures concern the room or site where the laser is used, and more specifically the areas where direct and reflected radiation travels, so as to prevent dangerous propagation for people and, where applicable, equipment. These measures are also aimed at organizing the operation of the equipment in the same way.

• Wherever possible, laser operation should be carried out in a room or area reserved for this purpose, enclosed or delimited.
• It is advisable to provide good lighting in rooms where the laser is used, to reduce pupil aperture.
• Accesses to the premises and their openings to the outside must not be located in the axis of a direct beam.
• The floor must be free of obstacles.
• The causes of accidental reflection and scattering of the laser beam must be eliminated (badly placed glass, furniture or objects with polished surfaces). Paintwork (walls, partitions, ceilings, etc.) and floor coverings should preferably be matt. Diffuse reflections from class 4 lasers are considered dangerous and treated as such.
• Eliminate the possibility of beam impact on flammable materials (wood, paper, fabrics or plastics), which can cause fires at power densities of the order of a few W.cm-2 applied for a few seconds.
• Access to laser emission areas must be marked using the appropriate signs (Figure 33). This signage is supplemented by an indication of the class of laser equipment.

LASER BEAM PATH

• The orientation of the laser must not be altered while it is transmitting.
• It is advisable to position the laser beam path at a different height from the eye of standing or seated persons.
• To avoid unwanted propagation, laser transmitters and optical elements placed in the path of the radiation must be fixed with suitable supports.
• Hazardous radiation paths (normal or abnormal, but foreseeable) must be totally enclosed by suitable shields. These are able to withstand the impact of an accidental direct beam up to the point of necessary intervention, and effectively protect operators during this time.
• Limit laser beam propagation. Free beam propagation is a hazard that must be controlled. Targets for laser radiation can be workpieces (which can generate unwanted reflections), the workpiece layout, or receivers of various kinds… In terms of safety, they will be considered as additional sources.
• Laser beam working areas must have matt, dark surfaces. Energy absorber materials must not be flammable when stopping Class 4 laser beams. In severe cases, “energy traps” or convex mirror reflections can be used, to distribute the energy over surfaces of sufficient size to absorb the energy without damage.
• The areas through which laser radiation passes must be clearly marked, all the more so as radiation can be invisible, and wearing safety goggles limits the perception of the visible beam which they protect the eye from. Points of emergence, reflection (normal or abnormal, but predictable), absorption or impact of laser beams must also be clearly marked.

OPERATING MEASURES

• Control of the surface or space where laser radiation is dangerous, including prohibition of access for all uninvolved persons during emission periods.
• Special measures: those present must not wear reflective objects (watches, rings, etc.).
• Emission control: the control panel should be located away from areas exposed to hazardous emissions. Class 4 lasers must be controlled by a control key, removed when not in use and held by a qualified person.
• A warning system will be installed to alert people who might enter a danger zone, before the start of the show.

Individual protection measures

The provision and effective use of personal protective equipment, such as goggles or gloves, is intended to :

• Make up for collective protection that is technically impossible or far too costly,
• Wait for collective protection to be put in place or introduce it,
• Complete collective protection,
• To intervene punctually and briefly.

EYE PROTECTION

• Persons present must always wear suitable safety goggles. (OEM version, without casing or during maintenance operations).
• To prevent optical damage, eyewear must bear the CE mark and comply with standard EN207-208. The CE mark certifies that the personal protective device complies with the essential requirements of the relevant European directive and satisfies the applicable certification procedures.
• As safety goggles are designed for a specific wavelength and maximum energy density, their use on lasers with different characteristics is extremely dangerous, as they no longer provide protection.
• The quality of protective equipment must be checked periodically. Goggles must be free of scratches and impacts.
• Wearing eyewear does not allow direct vision into the beam. Visual protection protects against accidental exposure to scattered or diffused reflections of laser beam energy for a maximum exposure of 10 seconds.
• All personnel using the laser must be informed of the risks involved, and are obliged to use the appropriate safety devices.

SKIN PROTECTION

• If your hands are likely to come into contact with unprotected parts of the laser beam path, you must wear non-flammable protective gloves.
• Knitted gloves are not suitable, as they can allow the beam to penetrate.

MEDICAL SUPERVISION

Such monitoring seems necessary for people operating with class 4 lasers. Its purpose is to establish the state of eyesight and fitness of persons before exposure, periodically and, after incidents, to detect and assess damage to the eyes, and possibly to the skin.

Other protective measures

PROTECTION AGAINST ELECTRICAL HAZARDS

• The voltages used in lasers, over and above the supply to certain low-voltage circuits, can be very high, on the order of several kV. Live parts (especially capacitor banks) must be inaccessible during operation. Access to these parts should only be possible if the power supply is disconnected and the capacitors discharged. The risk may remain for maintenance and repair personnel.
• The provisions of decree no. 88-1056 of November 14, 1988 concerning the protection of workers in establishments using electrical currents must be observed. Low-voltage laser equipment must comply with the specifications of standard NF C 15-100 “Installations électriques à basse tension”: Règles de mai 1991 and its addenda of December 1994 and December 1995.
• Access to laser emission zones will be signposted using signs complying with the French ministerial order of November 4, 1993, “Signalisation de sécurité et de santé sur les lieux de travail” (“Health and safety signs in the workplace”) and standard NF X 08-003 Symboles graphiques et pictogrammes – couleurs et signaux de sécurité” (“Graphic symbols and pictograms – colors and safety signs”) of December 1994. These accesses can be controlled, at least when lasers are in operation. In the case of laser equipment itself, this signage is supplemented by an indication of the equipment’s class and the information specified in standard NF EN 60825-1.

PROTECTION AGAINST CHEMICAL HAZARDS

The use of lasers on materials to be processed can lead to chemical pollution. This takes the form of aerosols or toxic gases resulting from the thermal degradation of these materials and/or substances that may have adhered to their surface (anti-corrosion coatings, traces of degreasing solvent, etc.).

In the event of the emission of inconvenient, unhealthy, irritating or toxic fumes, these must be collected at source, as they are produced, filtered and evacuated outside the work premises.

LaserKube must be connected to a system for extracting and treating fumes and particles when the machine is in use.