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Section XVII

Controls for Non-Beam Hazards

  1. Electrical Hazards
    The use of lasers or laser systems presents an electric shock hazard. Most lasers contain high-voltage power supplies and capacitors or capacitor banks that store lethal amounts of electrical energy. Exposures may occur from contact with energized components operating at potentials of 50 volts and above. These exposures most often occur during set up or installation, maintenance, modification and service when protective covers are removed.
    To reduce electrical hazards:
    • Lasers and associated electrical equipment must be designed, constructed, installed and maintained in accordance with the latest revision of the National Electric Code (NEC.)
    • When protective housings or covers will be removed, potentially exposing energized components, the following measures must be followed:
      1. Adhere to the University’s Lock Out Tag Out Procedure.
      2. Enclose high voltage sources and terminals whenever possible.
      3. Turn off power and ground all high voltage points before working on power supplies.
      4. Check that each capacitor is discharged and grounded prior to working near the capacitor. (Capacitors must be equipped with bleeder resistors, discharge devices or automatic shorting devices.)
      5. Do not wear rings, watches or other jewelry when working with or near electrical equipment.
  2. Laser-Generated Air Contaminants (LGAC)
    Air contaminants may be generated when Class 4 and some Class 3b laser beams interact with matter. The quantity, composition and chemical complexity of the LGAC depend on the target material, cover gas and beam irradiance. Materials such as plastics, composites, metals and tissues may release carcinogenic, toxic and noxious air contaminants. Ozone is produced around flash lamps and can build up with high repetition rate lasers. Special optical materials used for far infrared windows and lenses may also release hazardous air contaminants.
    Concentrations of LGAC must be maintained below the exposure limits specified by OSHA, NIOSH or ACGIH. There are three major control measures to reduce the concentration of LGAC to acceptable levels:
    • Use local exhaust ventilation to remove the LGAC at the point of generation. Local exhaust ventilation should be vented to the outside.
    • Isolate the process whenever possible.
    • Respiratory protection shall be used only when engineering controls are not feasible. ehrs@ehrs.upenn.edu must be contacted prior to wearing a respirator. Refer to the University’s Respiratory Protection Program for more information.
  3. Collateral and Plasma Radiation
    Collateral radiation (radiation not associated with the primary laser beam) may be produced by system components such as power supplies, discharge lamps and plasma tubes. Radiation may be in the form of X-rays, UV, visible, IR, microwave and radiofrequency (RF.)
    When high power pulsed laser beams (peak irradiance of 1012 W/cm2 or greater) are focused on a target, plasma is generated that may also emit collateral radiation.
    Contact the LSO for evaluation of these hazards. A Health Physicist will evaluate hazards associated with ionizing radiation.
  4. Fire Hazards
    Class 4 laser beams can ignite flammable solvents, gasses and combustible materials:
    To reduce fire hazards:
    • Terminate laser beams with non-combustible materials
    • Bring only necessary materials into the laser area.
    • Store flammable and combustible solvents and materials properly and away from the laser beam.
  5. Explosion Hazards
    High-pressure arc lamps, filament lamps and capacitor banks may explode if they fail during operation. The laser target and elements of the optical train may shatter during operation.
    To reduce explosion hazards:
    • Enclose high-pressure arc lamps and filament lamps in housings that can withstand an explosion if the lamp disintegrates.
    • Enclose the laser target and optical train in protective housing during laser operation.
    • Ensure that capacitors are equipped with current-limiting devices and are shielded.
  6. Compressed Gases
    Hazardous gases are used in some laser applications including chlorine, fluorine, hydrogen chloride and hydrogen fluoride. Refer to Section VI of the Chemical Hygiene Plan for more information on compressed gas safety. Laboratories with compressed gases are required to have an SOP. See the Compressed Gas SOP in the Chemical Hygiene Plan.
  7. Laser Dyes and Solvents
    Laser dyes are complex fluorescent organic compounds that are dissolved in a solvent to form a lasing medium. Some dyes are highly toxic or carcinogenic. Most solvents suitable for dye solutions are flammable and toxic by inhalation and/or skin absorption.
    The following measures shall be followed when working with dyes:
    • Whenever possible, do not use dimethylsulfoxide (DMSO) as a solvent for cyanine dyes because it aids in the transport of dyes through the skin and into the blood stream. If DMSO must be used, wear gloves. Disposable nitrile gloves may be worn if prolonged contact with DMSO is not anticipated. Other glove choices include neoprene, natural rubber and butyl gloves. PVA and PVC gloves are not recommended for use with DMSO. See the Chemical Hygiene Plan Handling of Chemicals for more information.
    • Obtain material safety data sheets (MSDSs) for all dyes and solvents prior to working with them. MSDS resources are available on the EHRS website.
    • Prepare and handle dye solutions in a fume hood.
    • Use disposable bench covers.
    • Wear a lab coat, safety glasses and gloves. Contact EHRS for assistance with glove selection.
    • Pressure test all dye laser components before using dye solutions. Pay particular attention to tubing connections.
    • Install spill pans under pumps and reservoirs.
    • See the Chemical Hygiene Plan for more information regarding safe chemical work practices.
  8. Noise
    Noise levels from some lasers, such as pulsed excimer lasers, may be high enough to require hearing protection. A good rule of thumb is if it is difficult to conduct a normal conversation at approximately 3 feet away, hearing protection may be required. Contact EHRS for noise monitoring and assistance in selecting hearing protection.

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