The most lethal hazard associated with lasers is the high voltage electrical system required to power lasers. Several deaths have occurred when commonly accepted safety practices were not followed by persons working with high voltage sections of laser systems. The following is a list of recommended electrical safety practices:
- Do not wear rings, watches or other metallic apparel when working with electrical equipment.
- When working with high voltages, regard all floors as conductive and grounded.
- Do not handle electrical equipment when hands or feet are wet or when standing on a wet floor.
- Be familiar with electrocution rescue procedures and emergency first aid.
- Prior to working on electrical equipment, de-energize the power source. Lockout and tag-out the disconnect switch.
- Check that each capacitor is discharged and grounded prior to working in the area of the capacitors.
- Use shock preventing shields, power supply enclosures, and shielded leads in all experimental or temporary high-voltage circuits.
Many dyes used as lasing media are toxic, carcinogenic, and corrosive or pose a fire hazard. A material safety data sheet (SDS) must accompany all chemicals handled at the University of Iowa. The SDS will supply appropriate information pertaining to the toxicity, personal protective equipment and storage of chemicals.
Various gases might be exhausted by lasers or produced by targets. Proper ventilation is required to reduce exposure levels of the gas products below acceptable limits.
Cryogenic fluids are used in the cooling systems of certain lasers. As these materials evaporate, they replace the oxygen in the air; thus, adequate ventilation must be ensured. Cryogenic fluids are potentially explosive when ice collects in valves or connectors that are not specifically designed for use with cryogenic fluids.
Condensation of oxygen in liquid nitrogen presents a serious explosion hazard if the liquid oxygen comes in contact with any organic materials.
Although the quantities of liquid nitrogen used are small, protective clothing and face shields must be used to prevent freeze burns to the skin and eyes.
Compressed gases used in lasers also present potential health and safety hazards. Problems may arise when working with unsecured cylinders, cylinders of hazardous materials not maintained in ventilated enclosures, and gases of different categories (toxins, corrosives, flammables and oxidizers) are stored together.
Radiation other than that associated with the primary laser beam is called collateral radiation. Examples are X-rays, LTV, plasma, radio frequency emissions, and ionizing radiation. X-rays could be produced from two main sources in the laser laboratories: Electric-discharge lasers and high-voltage vacuum tubes of laser power supplies, such as rectifiers, thyratrons and crowbars. Any power supplies that require more than 15 kilovolts (kV) may produce enough X-rays to cause a health hazard. Interaction between X-rays and human tissue may cause a serious disease such as leukemia or other cancers, or permanent genetic effects that may show up in future generations.
UV and Visible
UV and visible radiation may be generated by laser discharge tubes and pump lamps. The levels produced may exceed the MPE limit and thus cause skin and eye damage.
Interactions between very high power laser beams and target materials may in some instances produce plasmas. The plasma generated may contain hazardous UV emissions.
Radio Frequency (RF)
Q switches and plasma tubes are RF excited components. Unshielded components may generate radio frequency fields that exceed federal guidelines.
Class 4 lasers represent a fire hazard. Depending on the construction material, beam enclosures, barriers, stops and wiring are all potentially flammable if exposed to high beam irradiance for more than a few seconds.
High-pressure arc lamps, filament lamps and capacitors may explode violently if they fail during operation. These components are to be enclosed in a housing that will withstand the maximum explosive force that may be produced. Laser targets and some optical components also may shatter if heat cannot be dissipated quickly enough. Consequently care must be used to provide adequate mechanical shielding when exposing brittle materials to high intensity lasers.
Laser Generated Airborne Contaminants (LGAC)
Air contaminants associated with the use of Class 3B and Class 4 lasers. LGACs result from the interaction of the laser beam with tissue or other materials and can include smoke, chemical vapors and aerosols containing biological contaminants. LGACs are generally only formed when target irradiance reaches 107 W/cm2. Local or area ventilation must be adequate to keep airborne contaminant levels below worker exposure limits. See UIHC Policy “Surgical Smoke and Aerosols” for further information.