February 14, 2002
This article reviews the OSHA and ANSI standards for using safety spectacles in the workplace, describes scratch-resistance and anti-fog coatings, describes safety spectacle protection from ultraviolet and infrared radiation, and provides tips for choosing and using safety glasses.
According to the National Society to Prevent Blindness, 400,000 eye injuries occur on the job each year. The Bureau of Labor Statistics says an estimated 60 percent of workers suffer eye injuries when they're not wearing any protection. These statistics demonstrate that everyone needs to be much more vigilant about their eye protection.
Today safety spectacles are available in fashionable styles to protect against almost any workplace hazard. However, like other personal protective equipment, the most effective safety spectacles are those that people actually wear.
Safety spectacles—as mandated by Occupational Safety and Health Administration (OSHA) Title 29 CFR, Part 1910.133—must conform to the requirements of the American National Standard for Occupational and Educational Eye and Face Protection (American National Standards Institute [ANSI] Z87.1-1989). An approved spectacle must have a "Z87" stamped on the temple area.
In addition to meeting or exceeding the ANSI Z87.1 requirements in the U.S., safety spectacles also must meet or exceed the Canadian Standards Association (CSA) Z94.3-1992 standard in Canada. CSA tests submitted products (third-party certification) and performs regular quality audits of manufacturers.
29 CFR 1910.133 also requires that safety spectacles provide "side protection when there is a hazard from flying objects." This usually is accomplished with the use of integrated, molded-in sideshields. Some spectacles are designed with built-in side protection on the temple or spectacle frame.
Almost all of today's protective eyewear lenses are made of optical-grade polycarbonate. In addition to being lightweight and impact-resistant, this material can be molded with a high degree of optical clarity, which is required by ANSI and CSA regulations.
Lens coatings play an important role in the effectiveness of safety spectacles. Polycarbonate lenses normally are hard-coated for added scratch resistance and longer lens life, or they can be coated for antifog properties.
Hydrophobic (fog-resistant) coating is applied by first dipping the lens into the coating and then baking it to create a permanent bond to the lens surface. The coating repels water molecules and creates a sheeting effect that reduces the moisture that normally would create fog on the lens.
Antifog coating also reduces static charges that attract dust and other particles. This, in turn, minimizes distortion and nearly eliminates lens damage from scratches during cleaning and maintenance.
In testing, antifog coating has been resistant to several chemicals, including such common workplace solvents as acetone, acetic acid (glacial), carbon tetrachloride, ethyl alcohol, formaldehyde (37 percent), hydrochloric acid (20 percent), isopentyl acetate, isopropyl alcohol, methylene chloride, methyl alcohol, tetrahydrofuran, toluene, turpentine, and xylene (mixed).
UV radiation is defined as electromagnetic radiation from 100 to 380 nanometers and is naturally present in sunlight. It also is present in welding, brazing, and cutting operations. Optical-grade polycarbonate is specifically formulated to absorb 100 percent of UV radiation up to 380 nm, but it does not make an effective sunglass material because of the high transmittance of visible light. Tinting can be added to block light and glare, creating a spectacle that can be used as a safety sunglass.
The ozone layer filters most of the UV radiation from the sun, but some still reaches the earth. Although small doses of UV radiation are not dangerous, it can have harmful effects on the eyes over time. The most common immediate, acute effect is photokeratitis, which causes a painful sunburn on the surface of the eye. Long-term problems may include the formation of cataracts.
IR radiation is invisible electromagnetic radiation with wavelengths greater than 780 nm and is felt as heat. IR night scopes use special light-gathering lenses that can detect and see IR "heat" being emitted from normally invisible objects.
IR radiation is most commonly produced in welding, cutting, and brazing operations, as well as in furnaces and molten metal production. Certain shaded lenses ranging from 1.7 to 12 can be used for these applications. The higher the number stamped on the lens, the greater the protection against IR and UV radiation. A shaded bronze lens, for example, has a shade 3 rating.
Clear and tinted lenses that offer protection against UV radiation cannot be used to protect against IR radiation. Only shaded lenses designed for IR protection can be used.
Both the ANSI Z87.1 and OSHA 1910.133 regulations contain selection charts for shaded lenses for welding, cutting, and related applications. The CSA Z94.3 standard also lists shaded numbers and their maximum transmittance values for UV, IR, and visible light transmission.
Various tinted lenses are available in many safety spectacle styles. Although these lenses absorb 100 percent of UV radiation, they are not shaded absorptive lenses. With the approval of a safety director, tinted lenses can be used both indoors for specialty purposes and outdoors as a safety spectacle.
An indoor-outdoor lens is designed to protect against both bright sunlight and harsh overhead lights. For example, it is helpful for workers who frequently move from a warehouse to an outside stocking area and vice versa. Dark tinted lenses are available to protect against blue light and short-duration electric arcs.
Tinted lenses should not affect color perception. True color gray (TCG) lenses are especially effective if a worker needs to see colors for electrical wiring applications, when encountering traffic signals, and so forth.
Mild soap or detergent and warm water is the best solution for cleaning safety spectacles. Solvents should not be used. Most eyewear can be disinfected or sterilized using a mild bleach solution.
For special lenses such as those with an antifog coating, a standard lens cleaner or a solution of mild detergent and warm water may be used. For drying, a soft cloth is the best choice. To avoid scratches, a dry lens never should be cleaned with a paper towel or untreated paper.
ANSI, 1819 L St., N.W., Washington, DC 20036, phone 202-293-8020, fax 202-293-9287, Web site www.ansi.org.
CSA, 178 Rexdale Blvd., Toronto, ON M9W 1R3 Canada, phone 416-747-4000, fax 416-747-4149, Web site www.csa-international.org.
U.S. Department of Labor, OSHA, 200 Constitution Ave., N.W., Washington, DC 20210, Web site www.osha.gov.
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