X rays

Some of the high voltage systems with potentials greater than 30 kV may generate X rays at significant dose rates. Plasma systems and ion sources operated at high voltages should also be checked for X rays. High power (kilojoule) electron pumped Excimer lasers can generate significant X-ray levels (300 mrad per pulse at 15 feet). These devices need to be checked by Health Physics upon installation to ensure adequate shielding is included.

Free electron lasers are driven by powerful radiation producing devices, which are Controlled Radiation devices regulated by the State. All users are required to be oriented concerning the ionizing radiation hazards and the protection systems and procedures associated with these devices.

Correlative radiations

Materials can be made incandescent when exposed to laser radiations. These incandescent spots are very bright and can cause serious photochemical injuries to the eyes. The laser protective eyewear may not protect against such exposures. Whenever possible, view such spots through suitable filters; use TV cameras, etc., as may be appropriate.

Fires

Keep flammables out of the beam line. Also, maintain segregation between reactive reagents in the lab. Call Environmental Health & Safety at 723-0448 for advice. Keep a fire extinguisher of the proper class for electrical fires readily accessible in the area.

Chemicals

Fumes and plumes produced when laser radiation vaporizes or burns a target material, whether metallic, organic or biological (may contain viable organisms such a viruses), may be hazardous. Adequate ventilation needs to be provided. Call Environmental Health & Safety at 723-0448 for assistance.

Many dyes and solvents used for dye lasers are toxic; some may be carcinogenic. When DMSO is the solvent, the dyes may be particularly hazardous, if spilled on the skin, because dimethyl sulfoxide (DMSO) promotes absorption through the skin. Manufacturers are required to supply Material Safety Data Sheets (MSDS) on each product. The MSDS is is to be accessible to workers. Many MSDSs are available on-line. If the MSDS cannot be located, contact Environmental Health & Safety at 723-0448.

Included below are some recommended controls for laser dyes from a report entitled, Laser Dyes, Hazards and Controls, from Lawrence Livermore National Laboratory (LLNL). Appendix E lists a number of laser dyes and their hazards (also prepared by LLNL.)

CONTROLS FOR HANDLING LASER DYES

"Potential exposures to dyes and solvents are most likely to occur during solution preparation. Failure of the dye laser's pressure system can also expose personnel, and can cause fires.

Recommended controls for handling dyes, preparing solutions, and operating dye lasers are as follows:

• During solution preparation, dye and solvent mixing should be done inside a chemistry fume hood. Mutagenic dyes should be weighed out in a glove box.
• Dampers can be used to adjust airflow turbulence to a minimum during delicate weighing-out of fine dye powders. If, because of airflow, dyes cannot be weighed out accurately, scales should be located inside suitable enclosures to limit the potential airborne hazard. Avoid creating dust.
• Gloves, lab coats, and eye protection should be worn. Avoid skin contact.
• During dye laser disassembly, use proper personal protective equipment and be alert to contaminated parts, e.g., dye filters. Be sure to cap off dye solution lines.
• Don't smoke, eat, or drink in dye mixing areas.
• Dye pumps and tubing/pipe connections should be designed to minimize leakage. Pumps and reservoirs (notorious for leaking) should be set inside spill pans. Tubing/pipe systems should be pressure-tested prior to using dye solutions and periodically thereafter. Dye solutions can be corrosive. Stainless steel heat exchangers are recommended.
• For waste disposal and spills, emphasis should be placed upon solvent characteristics since dye concentrations are low.
• Keep dye handling areas clean and segregated from other operations. Fortunately, the brilliant colors of dyes enable users to see spills from sloppy handling."

Keep all containers of solvents, solutions, and dyes tightly closed, clearly labeled, and stored in a cool, dry place. Keep oxidizers away. Appropriate dye container labels should read as shown in the specimen below:

SPECIMEN FOR LASER DYE LABEL

Hazardous Gases and Cryogenic Materials

Flammable gases, e.g., hydrogen, and oxygen tanks present significant hazards if proper handling, manifolding and storage precautions are not followed. Other hazardous gases may also require special handling and ventilation. Gas cylinders must be properly anchored with metal linked chains, fastened at the top and near the base of the tank to prevent falling. Such tanks can become high velocity projectiles and can cause significant property damage and injuries. Call Environmental Health & Safety for advice.

A number of laser systems utilize toxic gases (e.g., HF). These gases must be contained in approved ventilation and manifold systems. Environmental Health & Safety will provide information on approved systems.

Wear appropriate protective clothing and face shields when handling large quantities of liquid nitrogen (LN) or other cryogenic materials. The normal moisture and oils present on the skin will protect against a few drops of LN spilled on the skin, but large quantities can cause severe frostbite. LN and inert gases can displace air in a room or confined area and cause asphyxiation. Good ventilation is required in areas where these gases and cryogenic liquids are used.

Open dewars of LN can condense oxygen from the room air and cause fire or explosion hazards if the oxygen contacts a fuel.

Consult Environmental Health & Safety at 723-0448 regarding specifics.

Electrical Safety

Most laser systems involve high potential, high current power supplies. The most serious accidents with lasers have been electrocutions. There have been several fatalities related to lasers, nationwide. Make sure that high voltage systems are off and locked out, and especially that high-energy capacitors are fully discharged prior to working on a system. Beware that capacitors may have their charges restored after initial discharge. Systems should be shorted during repair or maintenance procedures. The discharge of large capacitors requires proper equipment and procedures because significant levels of stored energy can be released as heat or mechanical energy. Review and follow electrical safety sections of the Laser Institute of America's booklet, entitled, "Laser Safety Guide."

• Class 3b and 4 lasers should have a separate circuit and local cut-off switch (breaker) for the circuit.
• Label and post electrical high voltage hazards and switches. Clearly identify the main switches to cut-off power. Before working on a laser, de-energize the machine. Positively disconnect it, if there is more than one source of power, disconnect them all. Lock out and tag the disconnect switches so that power is not reconnected while you are working on the laser.
• It is good practice to have at least two persons in an area while working on high energy power systems.
• Keep cooling water connections away from main power and high voltage outlets and contacts. Use double hose clamps on cooling water hoses. Inspect cooling water hoses and connections and power cables and connectors periodically as part of a regular equipment inspection. Check with Environmental Health & Safety on the proper installation of cooling water lines.
• Where laser power supplies are opened or serviced by lab personnel, courses in cardiopulmonary resuscitation and in proper rescue techniques to follow in the event of electrocution are required for the staff who work in such areas. Cowell Health Services offers CPR courses.

Additional information on electrical safety found in Appendix F and help is available from the University's Environmental Health and Safety Department at 723-0448.