Safety Glasses Information
For many jobs involving flying debris, safety glasses are a necessity. But safety glasses come in two types, basic and high impact, and can be both prescription and non-prescription, or plano, glasses. How do you know what kind of glasses you need for your job? Although an employer should inform you whether you will need basic or high impact glass, carpenters, plumbers and pipe fitters, machinists, millwrights, and laborers all need high impact eye protection.
All safety glasses need to meet high standards of impact resistance for both the lens and the frame. Both OSHA and ANSI Z87.1-2003 have detailed standards for safety glasses. However, although the lenses for all safety glasses are now mostly made of polycarbonate instead of glasses, non-prescription lenses for high-impact glasses are naturally structurally weaker. While polycarbonate has half the weight of glass and more impact resistance, thinner lenses for prescription safety glasses are still allowed in many work conditions, as long as the thinner lenses meet high impact safety requirements. Thinner prescription safety glasses lenses are less than 3mm thick, which was the previous standard for all prescription safety glasses.
Glass lenses for safety glasses have to go through series of safety tests to be labeled as either basic or high-impact lenses. To meet the requirements as a basic safety glasses lens, the lenses have a one-inch diameter steel ball dropped onto them from a height of 50 inches. To pass this test, the lenses must not crack, chip, or break. Plastic safety glasses lenses, however, are tested in a batch and not individually like glass lenses. To meet high impact requirements, the lenses need to pass a high velocity test in which a quarter-inch diameter steel ball is shot at the lenses with a speed of 150 feet per second, and the lenses must to crack, chip, break, or become dislodged from the lens holder.
Safety glasses frames have to go through a similar series of tests to determine their durability. One test is a high mass impact test, in which a one-inch diameter steel projectile weighing 17.6 ounces is dropped through a tube from a height of 50 inches onto the lenses and frame. To pass this test, the frame must hold the lenses in place and no piece can become detached from the inner surface of the safety glasses. Another similar test is the high velocity impact test, in which a quarter-inch steel ball is shot at the frame and lenses with a speed of 150 feet per second from a distance of ten inches at different angles. The glasses need to pass the same standards as the high impact mass test. In addition, safety glasses frames need to pass a series of durability tests including flammability and corrosion resistance.
After all frame and lenses tests, the safety glasses are then labeled to indicate whether they are basic or high impact glasses. Plano safety glasses are given labels of Z87 for basic and Z87+ for high impact glasses. Prescription safety glasses are labeled as Z87-2, with this label displayed permanently on the front of and on both temples of the frame. For the actual lenses, high impact safety lenses are given a + mark. Other lens marks include a V for photochronic lenses and S for special tint, as well as a number to indicate the amount of light reduced by the tint. For jobs in which workers are exposed to large amounts of light and heat, such as in welding, these safety sun glasses, or UV safety glasses, need to be numbered from 1.5 to 3.0. For more intense welding jobs like arc welding, the UV safety glasses need to be labeled with numbers 10 to 14.
Whether the glasses are prescription bifocal safety glasses or plano safety glasses by Uvex, Pyramex, Harley Davidson, or Crews, all safety glasses needs to pass these safety tests. In addition, for some occupations, the safety glasses dont protect alone. Some other eye and face protection equipment might be needed in addition to glasses, including side shield, a half or full face shield, and goggles.
