Impact Resistance: Protective Eyewear, ANSI & Z87
A look at the standards, and how they compare
By Philip M. Johnson, Honeywell Safety Products.
Background
Z87 Glasses with Impact ResistanceAround the world, safety standards exist for assessing the performance of protective eye and face products, including requirements for impact resistance. While the test procedures may differ somewhat from region to region, the intent is to measure impact strength of the entire protector, and to set criteria for minimum levels of performance. However, one test that has been harmonized across many key regional standards is the high velocity test conducted with a ¼ inch steel ball.
Selecting eyewear that meets or exceeds a variety of standards will afford reliable protection against hazards that are present in the workplace.
US – ANSI Z87.1
For protective eyewear meant for industrial or occupational use in the US, the governing document is ANSI Z87.1, and it has been in existence, through several iterations, for almost 40 years. OSHA in its 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/face protection is needed, such protection must be provided, and it must comply with this ANSI standard.
The current edition of the standard is Z87.1-2010. In the standard, eye protectors are either non-impact or impact rated devices. Impact rated protectors must meet the established high mass and high velocity tests, and defined, continuous lateral coverage. 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 gm (1.1 lb) 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 remain 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 6 specified impact points, where the projectile is a ¼ inch steel ball traveling at specific speeds depending upon the type of protector. For spectacles, the velocity is 150 ft/sec or 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.
In the United States, compliance with the standard is self-certified, based on test results generated by the manufacturer as part of its initial design and ongoing Quality Control procedures. No independent certification is required. Products meeting the standard will carry a “Z87+” marking on the lens(es) and frame.
Canada – CSA Z94.3
In Canada, the pertinent standard is Z94.3 developed by the Canadian Standards Association (CSA). Impact performance is assessed with the ¼ inch steel ball traveling at 46.5 m/sec or 152 ft/sec. Impact points that must be evaluated include the midpoint of the protector, as well as multiple frontal and lateral locations, some of which duplicate those assessed for Z87.1. Other points are selected to test areas of the protector that could be vulnerable to impact such as where the lens attaches to the frame, where the temple pieces attach to the frame or where thin material sections are present. These sites will vary with the design of the product, providing a thorough evaluation of its ability to provide protection. Failure criteria are similar to those in ANSI Z87.1.
A manufacturer may test the products on its own, or as an option may submit products to CSA International to have them tested and thus “third party” certified as being in compliance. In the latter case, a product in conformance may be marked with the CSA logo, a recognized Quality Mark in Canada. It can be compared to marks such as Underwriter’s Laboratory (UL). Certain manufacturers, such as Honeywell Safety Products (formerly Sperian Protection), are authorized by CSA International to test products on its behalf because their laboratories have been audited to a strict set of guidelines. This allows the CSA logo to be marked on the product after review and acceptance of the test results by CSA.
Military Ballistic Performance
The various branches of the U.S. military have recognized for many years that eye injuries are an inevitable by-product of their 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. Protection is required for ballistic impact protection, chemical resistance and for radiation protection from sunlight and high energy lasers. Over the past 8 to 10 years, the U. S. Army particularly has championed the use of high performance spectacles as general issue gear for all deployed personnel. A small group of products including Uvex Genesis® spectacles have been approved and have seen extensive use in Afghanistan and Iraq where improvised explosive devices (IEDs) are a constant threat.
The Army specifies that protective eyewear comply with Military Standard 662 which outlines a number of ballistic fragmentation tests for different categories of body armor. The test consists of firing a special shrapnel simulating projectile at a specified velocity. The fragment is cylindrical and has an angled face that will burrow into the product. For ballistic spectacles, the fragment is 0.15 caliber and the velocity of the projectile is 650 +/- 10 ft/sec (440 mph). In this case, the test protocol specified is “V0” (V-Zero). This means that no (zero) impact failures are allowed at the velocity specified. The spectacle is impacted once, at a point coinciding with the center of either the left or right eye. The lens cannot fracture, nor can the projectile penetrate to the eye. The impact energy of this test is about 7 times that of a ¼ inch steel ball traveling at 150 ft/sec.
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 V0 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 standards test. While many spectacles can meet the minimum performance of industry standards, higher performing products offer better protection to give you a fighting chance in case of unforeseen accidents. (No product is unbreakable or impenetrable given high enough impact energy, and additional protection such as goggles or face shields may be necessary based on the workplace hazard assessment).
Additional protection will make sense, and certainly be appreciated, in other applications including EMS, law enforcement and homeland security. The proper combination of design, materials and controlled manufacturing processes will yield superior impact protection in products that are at the same time stylish, comfortable and a great value given the level of protection delivered.
Selecting eyewear that meets or exceeds a variety of 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 upon for hours of safe and secure use in most industrial and occupational settings.
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