Laser systems manufactured or marketed in the United States for the Army are to comply to the provisions of the Radiation Safety Performance Standards issued by the Food and Drug Administration (FDA). If the laser product is unable to comply with the Federal Standard, then a military exemption may be possible. For more information on military exempt lasers, please see our page, "Military Exempt Lasers".
- It is important to remember that laser hazards exist only along the beam path.
- The eye and skin are two parts of the body most susceptible to a laser injury.
- For lasers that are focused by the eye (400-1400 nanometer (nm)), very little power is required to cause injury due to the concentration of the laser light by a factor of approximately 100,000 times. This is similar to burning a piece of paper by focusing sunlight with a magnifying glass.
- In addition to the focusing by the eye, wavelengths greater than 700 nm are invisible. Since a person cannot see these wavelengths, he or she may be exposed to the beam longer than to a visible wavelength laser beam. Visible lasers would be uncomfortably bright to view and the exposed individual would turn away. For lasers outside the "retinal hazard" region (IR wavelengths > 1400 nm), the laser radiation is absorbed mostly in the cornea and does not present a retinal hazard. These wavelengths permit higher irradiances or radiant exposures due to the laser energy not being focused by the eye, but these wavelengths are not necessarily "eyesafe".
For more information on hazards present from laser overexposure, the table below is split into groups of wavelength along with columns for eye and skin specific hazards.
180 nm – 280 nm (UV-C)||Photokeratitis||Erythema|
280 nm – 315 nm (UV-B)|||||
315 nm – 400 nm (UV-A)||Photochemical cataract||Pigment darkening|
400 nm – 780 nm (Visible)||Photochemical and thermal retinal injury|||
780 nm – 1400 nm (IR-A)||Cataract, retinal burn||Skin burn|
1.4 μm – 3.0 μm (IR-B)||Aqueous flare, cataract, corneal burn|||
3.0 μm – 1 mm (IR-C)|
Corneal burn only
Some of the terms in the table above may be defined as:
- Photokeratitis is commonly known as "welder's flash" since this wavelength is emitted from arc welding activities. These wavelengths are also emitted by the Sun. Photokeratitis affects the cornea with some symptoms being pain, redness, tearing, swelling, and eyelid twitching.
- Erythema is inflammation of the skin leading to a reddish coloration and surface irritation. Erythema can also occur if you are outside too long without applying sunblock, also known as sunburn. Since the wavelengths that cause sunburn when outside are the same as certain laser wavelengths, the reddening and pain of the skin due to exposure is a similar effect.
- Photochemical cataracts are cataracts formed due to a photochemical effect as opposed to a thermal one. A chemical reaction caused by UV absorption of the lens leads to clouding of the lens, known as a cataract.
- Aqueous flare is undesirable scattering of light in the aqueous humor, which is found between the iris and the cornea. This scattering, or flare, is caused by elevated protein concentration in the aqueous humor which, in this case, is from an IR laser overexposure. The effect is similar to lens flare seen in movies, though not as entertaining.
Lasers are classified by their degree of potential hazard. The 7 laser classes are listed below:
1||Emit at levels that are not hazardous under any viewing or maintenance conditions. However, as a matter of good safety practice, avoid intrabeam viewing.|
1M||Emit at levels that are not hazardous under unaided viewing conditions, but could be a hazard for intrabeam viewing through magnifying optics. |
2||Emit in the visible portion of the electromagnetic spectrum and are a potential eye hazard only for prolonged intrabeam viewing. The aversion response, including the blink reflex, would normally prevent overexposure.|
2M||Emit visible laser wavelengths and are not a hazard for short exposure durations for unaided intrabeam viewing. A Class 2M laser is hazardous for intrabeam viewing through magnifying optics within the reported hazard distances and requires a "caution" label. The laser output cannot exceed the Class 3B AEL for optically aided viewing.|
3R||Emit at levels that are potentially a hazard for direct intrabeam and specular reflection viewing. Diffuse reflections are not normally hazardous. |
3B||Emit at levels above Class 3R lasers but less than Class 4 lasers and are a hazard for direct intrabeam and specular reflection viewing. Diffuse reflections are not normally hazardous. Class 3B lasers are also possible a skin hazard. |
4||Emit at levels that are hazardous for direct intrabeam exposure and some can produce a hazard from diffuse reflections. Class 4 lasers are also possible a skin hazard. They may also produce fire, material damage, laser generated air contaminants, and hazardous plasma radiation.|