Radiation and Laser Safety

Transcription

1 Radiation and Laser Safety Introduction The increased use of lasers in science classes may pose a potential hazard to students and teachers. With the proper safety precautions, the laser can be a valuable tool for science teaching and can be operated with a minimum risk to teachers and students. Following are considerations which must be taken into account when using such devices. Individuals using radiation apparatus or radioactive substances must first possess a radiation licence. Note - Prescribed radiation apparatus, sealed source devices and premises where a radioactive substance not contained in a sealed source device is kept or used must be registered with the EPA. Identified Risks and Hazards Lasers emit intense, coherent, electromagnetic radiation that is potentially dangerous to the eye and skin. Other hazards associated with lasers, that the laser operator must be aware of Copyright 2010 OnGuard Safety Training PTY LTD 1

2 include: Atmospheric Contamination Vaporized target material. Materials may include carbon monoxide, ozone, lead, mercury, lithium, and other metals. Gases from flowing gas lasers or by-products of laser reactions such as fluorine, hydrogen-cyanide, and many others, and gases or vapors from cryogenic coolants. Chemicals Chemicals, including dyes and solvents. Certain dye lasers have been shown to be carcinogenic, toxic, or otherwise hazardous. Cryogenic Coolants Cryogenic liquids, such as liquid nitrogen or hydrogen, may cause burns. Electrical Hazards The potential for electrical shock is present in most laser systems. Explosive Hazards The potential exists for explosions at capacitor banks or optical pump systems during the operation of some high power lasers. Explosive reactions of chemical laser reactants or other gases used within the laser laboratory could cause damage to equipment or injury to personnel. Jewelry The use of jewelry (watches, rings, etc.) is often an overlooked source of exposure to a beam reflected by a mirror-like surface. Ultraviolet Radiation Either direct or reflected from flash lamps and cw laser discharge tubes may cause eye injury. Usually, ultraviolet radiation is a problem only when quartz tubing or windows are used. Visible Radiation (non-laser) High luminance radiation emitted from unshielded pump lamps may cause eye injuries. X-rays - Potentially hazardous X rays may be generated from high voltage (over 15kV) power supply tubes. Copyright 2010 OnGuard Safety Training PTY LTD 2

3 Pre- operational Safety Gloves Ensure that gloves are made of a material compatible with the chemicals being used and ensure that they are of a suitable thickness. Mask Always ensure that masks seal effectively and with reusable/cartridge masks a fit test is required. Laser Goggles Must be of the correct wavelength and sufficient optical density for the type and class of laser used. Ensure that the surface integrity is not compromised. Lab Coats Should be worn when working with chemicals or contaminated or dirty equipment to provide greater protection to your clothing and skin. Footwear Appropriate footwear is required in laboratories, even when you are not working with chemicals or carrying equipment. You should not wear flip-flops or sandals in a lab as these leave you exposed to slips, trips, chemical burns, cuts and crushes. Laboratory Environment The illumination in the area should be as bright as practicable in order to constrict the eye pupils of users. The laser should be set up so that the beam path is not at normal eye level. i.e. so it is below 1.35 mts or above 1.95 mts. The potential for specular reflections should be minimized by shields and by removal of all unnecessary shiny surfaces. Copyright 2010 OnGuard Safety Training PTY LTD 3

4 Windows to hallways or other outside areas should be provided with adequate shades or covers. The main beams and reflected beams should be terminated or dumped. The active laser never should be left unattended unless it is a part of a controlled environment. Good housekeeping should be practiced to ensure that no specular reflector is left in or near the beam. Warning devices should be installed for lasers with invisible beams to warn of operation. Operating Safely Top Working with Laser Equipment Never look directly into a laser beam, even from a distance. A laser beam usually cannot be seen unless thee are airborne particles such as dust or smoke to provide scattered reflective surfaces. With some lasers, the beam cannot be seen even under these conditions. Do not rely upon tinted glasses, sunglasses or other protective devices unless the filtering medium has been designed to attenuate the specific wave length produced by the laser in question. There is no single glass filter which will protect at all laser frequencies. Never leave an activated laser unattended. An unsuspecting person may accidentally look into the beam, with resulting retinal damage. A warning sign should be posted when a laser is in operation. Copyright 2010 OnGuard Safety Training PTY LTD 4

5 Keep the rooms lighting at a high level (about 2150 lux) when operating the laser. This will tend to keep the eye pupil small and minimize the possibility of retinal damage due to inadvertent exposure. Never shine a laser beam on any reflective surface. The reflections may approach direct beam intensities. The average science laboratory is an extremely dangerous place to operate a laser because of the presence of laboratory gas and water fixtures, which usually are chromium plated with a high reflective surface. It is difficult, if not impossible to predict the angle of reflection because of the irregular shape of the fixtures. Special care must be also taken with watch crystals, rings, metallic watch bands, tools, glassware, door knobs, screw heads and other reflective objects. The floor, bench tops and cabinet should be covered with a dark, light diffusing material. The laser should not be operated in a room contaminated with smoke or dust, nor out of doors in rain, snow, fog, or heavy dust. Potentially dangerous secondary specular radiation may result. The flash tube of a pulsed laser should be shielded to prevent any one from looking directly at the tube when it fires. Intense light in the white, ultraviolet and infrared portions of the spectrum are produced which also may cause retinal damage. A safe laser operating procedure should be established. Prepare a checklist and follow it precisely each time the laser is used. Copyright 2010 OnGuard Safety Training PTY LTD 5

6 Operate the laser only under direct supervision of the supervisor or a qualified paraprofessional. Keep a record of the times of activation and the identities of the person present. A disarming device should be attached to the laser circuit. This device should be arranged so that the laser cannot be fired when the disarming device is removed. The teacher can remove the device or one of its components when he/she does not wish the laser to be activated. Never aim the laser beam toward windows or doorways, so that the people outside the room will not be exposed. Maintenance Storage A laser should be isolated from areas where the uninformed and curious cannot be attracted by its operation. Doors should be closed or locked to keep out unwanted onlookers. Where practical, the laser system or beam should be enclosed to prevent accidental exposure to the beam. Operating Procedures Safe Behavior around Laser Equipment Avoid looking into the primary beam at all times. Do not aim the laser with the eye - direct reflections could cause retinal damage. Avoid looking at the pump source. Clear all persons from the anticipated path of the beam. Copyright 2010 OnGuard Safety Training PTY LTD 6

7 Before operating the laser, warn all persons of the potential hazard, and ensure all safety measures are satisfied. Be especially cautious around lasers that operate at frequencies not visible to the human eye. Do not wear bright, reflective jewelry or other objects. Use proper eye protection. No matter how good the glasses, no protection is provided unless they are worn. All safety glass lenses may shatter, and all plastic lenses may melt when the maximum irradiance or radiant exposure for the particular lens is exceeded. Laser safety glasses may not provide eye protection with other than the laser for which they are specified, unless the frequency produced is the same and power output is not greater. Copyright 2010 OnGuard Safety Training PTY LTD 7