Basic Hazards from Laser Equipment
1. Eye -- Damage can occur from both acute and chronic exposure to laser radiation depending on the wavelength and exposure levels. Corneal and/or retinal burns can result from acute overexposure. Cataracts and/or retinal injury may be possible from chronic exposure to excessive levels.
Damage to the retina can result from visible and near-infrared radiation, (400 to 1400 nm). Light directly from the laser or reflection from a mirror-like surface entering the eye can be focused to an extremely small image on the retina due to the focusing effects of the cornea and lens.
Laser radiation in the middle-ultraviolet, (200 to 315 nm), and far-infrared, (3 micrometer to 1 mm), produce damage principally at the cornea.
Radiation in the near-ultraviolet, (320-390 nm), and middle-infrared, (1.4 -3 micrometer), passes through the cornea with little damage but effects the lens behind the cornea.
Therefore you can see that the tissues of the eye are susceptible to various forms of laser radiation and should be protected by appropriate eye protection depending on the wavelength of the laser emission.
2. Skin -- Burns can result from acute exposures to high levels of optical radiation. Some specific ultraviolet wavelengths can cause carcinogenesis of the skin.
Erythema, (sunburn), skin cancer and acceleration skin aging are possible from exposure of laser radiation in the range of 0.2 to 0.28 micrometer. Chronic exposure of 0.28 to 0.4 micrometer wavelength radiation can cause increase pigmentation. Photosensitive reactions are possible from wavelengths from 0.31 to 4 micrometer. And skin burns and excessive dry skin effects are possible from radiation in the range of 0.7 to 1 micrometer.
Even though skin effects have been considered of secondary importance from a safety standpoint, cases of skin damage has been increasing due to the increase use of lasers emitting ultraviolet light and high-power lasers.
3. Chemical Hazards -- Reactions induced by lasers can release hazardous particulate and gaseous products. An example of this occurs in material processing such as laser welding, cutting, and drilling which can create potentially hazardous fumes and vapors. General ventilation safety procedures should be used when lasers are used in this manner. 4.Electrical Hazards -- Lethal electrical hazards are particularly present when high-power laser systems are used. When using any high-voltage power supply, whether lasers or another systems, always practice commonly accepted safety procedures. 5.Other Secondary Hazards -- High-power lasers and lasers with continuous-wave output with power well above one-half watt have the potential to cause fire hazards. Another hazard associated with these types of lasers is working with cryogenic coolants such as liquid nitrogen. Skin contact can cause burns, improper plumbing can cause explosion, and insufficient ventilation can result in displacement of oxygen by the liquified gas vaporizing.
Americal National Standards Institute Laser Classification
Class Properties 1 Exempt lasers or laser systems that cannot, under normal operation conditions, produce a hazard. 2 Low power visible lasers or laser systems which, because of normal human aversion responses, do not normally present a hazard, but may present some potential for hazard if viewed directly for extended periods of time. 3a Lasers or laser systems that normally would not produce a hazard if viewed for only momentary periods with the unaided eye. They may present a hazard if viewed using collecting optics. 3b Lasers or laser systems that can produce a hazard if viewed directly. This includes intrabeam viewing or specular reflections. Except for the high power class 3b lasers, this class laser will not produce a hazardous diffuse reflection. 4 Lasers or laser systems that can produce a hazard not only from direct or specular reflection, but also from diffuse reflection. In addition, such lasers may produce fire hazards and skin hazards.
Since 1976 Federal law requires the manufacturer of lasers to provide the classification for all lasers produced. If the laser is changed by the user, the classification must be determined and made known to all users.
Laser Safety Rules
Class 1 Lasers
1. A warning sign indicating the laser classification should be placed in a visible location on the laser.
Class 2 Lasers
1. Do not stare at the laser or permit any person to stare at the laser beam.
2.Do not point the laser at a person's eye.
Class 3 Lasers
1. Never aim a laser beam at a person's eye.
2.Use proper safety eyewear if there is a chance that the beam or hazardous specular reflection will expose the eyes.
3.Only experienced personnel should be permitted to operate the laser. Never leave an operable laser unattended if there is a chance that an unauthorized person may attempt to use it. A key switch should be used. A warning light or buzzer should indicate when the laser is operating.
4.Enclose as much of the beam path as possible.
5.Avoid placing the unprotected eye along or near the beam axis as attempted in some alignment procedures since the chance of hazardous specular reflection is greatest in this area.
6.Terminate the primary and secondary beams if possible at the end of their useful paths.
7.Use beam shutters and output filters to reduce the beam power to less hazardous levels when the full output power is not required.
8.Make sure that any spectators are not potentially exposed to a hazardous condition.
9.Attempt to keep laser beam paths above or below either sitting or standing position eye level.
10.Operate the laser only in a well-controlled area. That is, in a closed room with no windows and controlled access.
11.Label lasers with appropriate Class III danger statements and placard hazardous areas with danger signs.
12.Mount the laser on a firm support to assure that the beam travels along the intended path.
13.Assure that individuals do not look directly into a laser beam with optical instruments unless a adequate protective filter is present.
14.Eliminate unnecessary specular (mirror-like) surfaces from the vicinity of the laser beam path.
Class 4 Lasers
1.Enclose the entire laser beam path if at all possible. If this is done, the laser device could be considered to be a less hazardous classification.
2.Confine indoor laser operation to a light-tight room with interlocked entrances to assure that the laser cannot emit when a door is open.
3.Insure that all personnel wear adequate eye protection, and if the laser beam irradiance represents a serious skin or fire hazard that a suitable shield is present between the laser beam and the any persons in the room.
4.Use remote firing and video monitoring or remote viewing through a laser safety shield where feasible.
5.Use beam traverse and elevation stops on outdoor laser devices to assure that the beam cannot intercept occupied areas or intercept aircraft.
6.Use beam shutters and laser output filters to reduce the laser beam irradiance to less hazardous levels whenever the full beam power is not required.
7.Assure that the laser device has a key-switch master interlock to permit only authorized personnel to operate the laser.
8.Install appropriate signs and labels on entrances, switches and anywhere an unauthorized person might mistakenly activate the laser.
9.Remember that optical pump systems may be hazardous to view and that once optical pumping systems for pulsed lasers are charged, they can spontaneously discharged, causing the laser to fire unexpectedly.
10.Use dark, absorbing diffuse, fire-resistant targets and backstops where feasible.