The most serious hazard associated with lasers is the electrical hazard from the laser power source. Several fatalities have occurred because of this hazard. Most laser power supplies contain severe electrical hazards. They often contain high voltages and energy storage capacitors and may also include water cooling. It is important that only qualified personnel ever work with energized laser power supplies and that lock-out/tag-out and approved procedures are always followed.
Bioeffects of 60 Hz AC
Relative Bioeffects Resulting from Exposure to Increasing Current
0.5 mA – No sensation usually felt with contact.
1.0 mA – A slight tingling felt with contact (perception threshold).
1.5 mA – Shock clearly felt (no pain or loss of muscle control).
7.5 mA – Painful shock (no loss of muscle control).
10 mA – Let-go threshold (loss of muscle control).
20 mA – Severe shock, hard to breathe, severe muscle contractions.
30 mA – Respiratory paralysis (frequently fatal if no CPR).
75 mA – Fibrillation threshold for 0.5% of exposed persons.
250 mA – Fibrillation threshold for 99.5% of exposed persons.
Electrical Hazard Contributors and Precautions
- Grounding – recommended for optical tables
- Grounding Plugs Cut-Off – replace before using
- Electrical Cords – replace frayed, torn cords, uncovered, improperly insulated terminals
- Cooling Lines – consider placement with respect to electrical
- Excessive heat build-up that is hot to touch – notify maintenance
- Fire Extinguishers – keep a fire extinguisher nearby rated for electrical fires
- Flammable Liquids/Materials – should be kept clear of possible ignition sources
- Hidden “power-up” warning lights – should be clearly visible and unobstructed
- CPR Training – highly recommended
- Capacitors – ensure capacitors are properly discharged and grounded prior to service
- Housekeeping/Organized Work Space – organize excessive cords on floors to prevent trip hazards – remove tools and clutter to prevent reflection/fire hazards
- Lock-out/Tag-out – should be performed before service and maintenance
- Qualified Electricians – The maintenance shop should be directly involved for any equipment service including new installation or modification of existing equipment.
Class 4 laser beams represent a fire hazard which includes irradiances of ten watts per square centimeter (10 W/cm2) or beam powers exceeding half a watt (0.5 W). In some situations, higher powered Class 3b lasers close to Class 4 can ignite materials as well. A fire extinguisher rated for electrical fires should be kept in close proximity and be readily accessible. Flammable liquids, materials, and potential ignition sources should be kept clear of the beam path.
Laser curtains and barriers should meet NFPA 701 fire protection or equivalent criteria as determined by Fire Prevention Services. EHS will also evaluate the barriers/curtains for proper placement, penetration times, and resistance to smoke production and open fire. A list of approved vendors for curtains and barriers can be found here.
High-pressure arc lamps, filament lamps, and capacitor banks in laser equipment can present possible explosion hazards which can be contained by ensuring they are within appropriately rated protective hazard. Precautions should be taken when service or maintenance of these items is required.
Target materials that can potentially shatter or explode should be enclosed to prevent injury to operators and personnel. A preventative maintenance schedule should be in place to prevent accumulation of dust that has collected in ventilation systems serving laser processes.
Non-Laser Radiation (NLR)
Collateral radiation is any electromagnetic radiation (except the laser radiation itself) that is emitted by the laser and can include ultraviolet/blue light hazards from laser cutting/welding operations, flashlamp light leakage, soft x-rays from greater than 15 kV electrical components, and even ionizing radiation from higher peak irradiance (1016 W/cm2) focused on a target. EHS Radiation and Laser Safety should be consulted to provide additional control measures.
Robots can punch holes in protective housings, pin personnel, damage the beam delivery system or direct a laser beam at operators or personnel and should be kept within an EHS approved operating envelope with an emergency stop button nearby. Mechanical interlocks within established angles of operation and geometry shall be required. The installation should conform to recommendations contained in the latest version of ANSI/RIA R15.06; Standard for Industrial Robots and Robot Systems-Safety Requirements.
Fragment hazards are possible cleaving fibers during splicing operations. Small lengths or particles of optical fiber material can pose a risk of irritation, infection, or injury. Consider the use of finger guards, gloves, or shields when cleaving. Adhesive tape can be used to pick up used particles or splices. Collect discarded fibers and place in a suitable container to avoid embedding in clothing, skin, eyes, or under finger nails.
Nanoparticles are small enough to pass through the blood-brain barrier, be transported deep into the lungs and tissues, and translocate between organs. The greater surface to volume ratio introduces new hazards not normally present in the larger agglomerations of these materials such as increased flammability or toxicity. Reasonable care should be taken to protect against these hazards during laser ablation processes. The EHS Occupational and Laboratory safety groups should be consulted if working with or producing nanoparticles.
Noise levels can be a concern or a nuisance with certain pulsed excimer and transversely-excited atmospheric (TEA) carbon dioxide lasers. Consult EHS Occupational and Laboratory safety for assessment and control measure recommendations.
Laser generated air contaminants (LGAC), compressed gases, dyes and solvents and assist gases can be present in lasers. Exhaust ventilation, isolation of the process, and respiratory protection should be considered when working with chemicals and lasers together.
Laser Generated Air Contaminants (LGAC)
Air contaminants can be generated when certain Class 3b and Class 4 lasers interact with matter and industrial hygiene practices should be employed. Re-circulation of LGAC[‘s should be avoided where-possible by using exhaust ventilation.
Hazardous gases are used in some applications and exhausted gas cabinets may be required depending on the severity of the hazard. As a general rule of thumb any compressed gas having an HMIS or NFPA 704 hazard rating of 3 for health, flammability, or reactivity usually meets the criteria requiring the exhausted cabinet and extra precautions such as sensors and alarms. In some situations, a hazard rating of 2 may also meet the criteria. SOP’s will be needed for these hazardous gases.
Compressed Gas Precautions
- Properly secure all cylinders. Should not be freestanding.
- Cylinders without regulators should have safety caps in place.
- Have provisions in place for remote shut-off or purging before disconnect/connect.
- Ensure cylinders are properly labeled. Don’t go by color.
- Do not clean regulators with organics such as oils.
- Store hazardous gases in exhausted gas cabinets.
- Use a gas cart to transport cylinders.
- Cryogenic gases will have additional training/precautions. See EHS training section.
Dyes and Solvents
Some lasers use specials dyes and solvents that could be flammable or toxic. Laser dyes should be prepared in a laboratory fume hood. Dye pumps and reservoirs should be placed in secondary containment to minimize leakage.
The use of dimethyl sulfoxide (DMSO) as a solvent for cyanine dyes should be discontinued if possible. DMSO aids in the transport of dyes through the skin and into the blood stream. If another solvent can’t be found use low permeability gloves.
These can include LGAC’s and infectious material such as airborne bacterial and viral organisms resulting from a high-powered laser beam interacting with tissue. Local exhaust ventilation within 1 cm of the source should be used whenever possible in additional to personal protective equipment (PPE) for respiratory protection.