Impact protection for eyewear
Answered by Philip Johnson, director of optical sciences and quality systems, Sperian Eye and Face Protection Inc., Smithfield, RI.
For protective eyewear meant for industrial or occupational use, the governing document is ANSI Z87.1. OSHA regulations (see CFR 1910.133) specifically cites Z87.1 as the minimum performance requirement for protective eyewear, effectively giving it the weight of law. Where a hazard assessment in the workplace indicates that eye or face protection is needed, such protection must be provided, and it must comply with this ANSI standard.
ANSI Z87.1 tests
The current edition of the standard is Z87.1-2003. Lenses in all protectors must, at a minimum, meet a basic impact requirement: A 1-inch steel ball is dropped free-fall through a tube from a height of 50 inches onto the lens surface. Products meeting this basic impact standard should be marked "Z87" on all major components.
Models can achieve "high" impact levels indicating elevated performance. The following "high" impact tests apply to lenses, as well as to the frames or product housing:
- A lens retention test is conducted via a "high mass" impact. A pointed 500-gram (1.1-pound) projectile is dropped 50 inches onto the complete protector mounted on a headform. No pieces can break free from the inside of the protector, the lens cannot fracture, and the lens must be retained in the frame or product housing. This test is a good measure of the product's strength, simulating a blow such as from a tool that slips from the work surface or when the lens collides with stationary objects.
- A high-velocity test is conducted at 20 specified impact points, where the projectile is a ¼-inch steel ball traveling at specific speeds depending on the type of protector. For spectacles, the velocity is 150 feet per second (102 mph). The pass/fail criteria are the same as for the high-mass test, plus no contact with the eye of the headform is permitted through deflection of the lens. This is meant to simulate particles that would be encountered in grinding, chipping, machining or other such operations.
Higher protection levels
Companies that need additional assurance and protection from impact should consider safety eyewear products that provide a higher level of impact protection than required by ANSI Z87.1. The various branches of the U.S. military have recognized for many years that eye injuries are an inevitable byproduct of many activities. This is true not just in combat situations, but in a variety of support activities on flight lines, in maintenance settings and in special operations.
The Army specifies that protective eyewear comply with military standard 662, which outlines a number of ballistic fragmentation tests for different classes of products. This test requires compliant spectacle products to withstand the impact of a high-caliber shrapnel simulating projectile moving at a velocity of 650 feet per second (440 mph). The impact energy produced in this test is about seven times higher than that of the ANSI high-velocity test. The lens cannot fracture, nor can the projectile penetrate to the eye.
One may wonder if this test is too extreme for eyewear meant primarily for industrial use. The way to look at this is the added level of protection and security afforded by products offering ballistic-level impact performance. For example, the obvious impact hazard may be particulate generated by an operation such as grinding. The less obvious threat is the explosion of the grinding wheel, which can send shards of material flying at speeds considerably higher than ANSI testing anticipates. Although many safety eyewear models meet the minimum performance of industry standards, higher-performing products offer better protection in the case of an unforeseen accident. Keep in mind that no product is unbreakable or impenetrable given high enough impact energy, and additional protection such as goggles or faceshields may be necessary.
Selecting eyewear that meets or exceeds prevailing industry standards will afford reliable protection against hazards that are present in the workplace. The eyewear will have been rigorously tested for impact resistance as well as other requirements, including optical performance and protection from radiation where needed. These products can be relied on for hours of safe and secure use in most industrial and occupational settings, and can provide an added level of protection and security – not to mention peace of mind – for the wearer and his or her safety manager.