Broken security glass that once covered the window of a security checkpoint, now abandoned. Belfast Northern Ireland.

Thickness Matters! Here’s what you need to know about your safety glass lenses.

October 29, 2021

Did you know that more than 700 Canadian workers sustain eye injuries every day? Flying particles and sparks from welding and grinding operations account for 70% of these injuries and more than 50% of these objects are smaller than the head of a pin1 and can be removed by an optometrist. The sad fact is that most of these injuries are completely preventable.

So, what are the chief reasons:

  1. A big reason for the eye injury rate is that employees don’t routinely wear safety eyewear when they should.
  2. Part of the reason employees they don’t wear their safety eyewear is that they are told to wear it without a proper explanation of how to wear it and why they should wear it.
  3. Confused by the rule requiring them to wear safety eyewear employees often ask, “What is it about safety eyewear that makes it safe?”. Is it just that the lenses are thicker, or the frames are heavier?

If you are confused about this, too, please read on.

Eye or face protection must be worn when workers could be exposed to flying objects or particles and debris, splashing liquids, molten metal and fume, and UV, Visible and IR radiation. The federal, provincial, and territorial occupational health and safety regulations requires workers to use safety eyewear that is compliant to the Canadian Standards Association (CSA) Eye and Face Protectors standards anytime work may pose a risk to the eyes.

The challenge arises when employees believe their trendy prescription streetwear or fashionable sunglasses offer the same protection as safety glasses. Simply put, streetwear glasses do not meet the same impact standards in part because of their construction and thickness. Although style may seem important, performance matters more. Plus, today’s range of types and styles of safety eyewear are more comfortable to wear and often available in many of the new fashion styles. The protection we’re talking about relates to safety glasses, googles, welding helmets, non-rigid helmets, face shields and certain types of respirator facepieces.

Typically, safety lenses are 2-3 mm thick depending on the material type and design. And although safety eyewear lenses are  thicker than  most non-safety eyewear lenses, there is more to it than that. Only lenses and frames made of approved materials go into manufacturing.

Safety eyewear frames may seem heavier because they are stronger than the frames of basic streetwear glasses. Another thing about safety eyewear that makes it safe is that all CSA approved equipment is subject to rigorous testing to confirm that it performs to intended standards. You’ll know you’re wearing the right safety eyewear when you can see the manufacturer’s markings on safety eyewear lenses and frames. These standards of performance and the requirements for employers to implement a formalized eyewear protection program are fully specified in two CSA Standards and called up in the legislation. These two Canadian Standards Association (CSA) standards related to safety eyewear are CSA Z94.3 Eye and Face Protectors and CSA Z94.3.1 Selection, Use and Care of Protective Eyewear.

Meeting the Standard requires the safety eyewear be exposed to a battery of tests including impact resistance, ignition/flammability, visibility, field of view, and other characteristics.  This Standard sets a minimum performance requirement for this range of performance tests including the “drop ball” and “high impact” test of the lens and frames. For example, to get the CSA approval, safety eyewear frame and lens must pass the impact of a 6.0 mm steel ball travelling at 50.9 m/s or a 6.4 mm steel ball traveling at 46.5m/s, without the frame failing or lens shattering. For those not familiar with m/s and mm measures, to get the CSA approval the safety eyewear has to stand up to the impact of a 1/4 inch ball bearing flying into it at over 180 km/hour. Both the frame and the lenses have to stand up to this test and further the lens and frame assembly have to be strong enough to prevent the lenses from detaching and being pushed into the wearer’s eyes.  Ordinary street-eyewear will not  meet this performance standard.

If an employee wears prescription eyeglasses they need to wear prescription safety eyewear. The CSA Standard specifies that prescription safety eyewear must be fitted by a qualified professional (e.g., a Doctor of Optometry or their knowledgeable staff). The Eyesafe program uses the clinics of optometrists to work with employees to ensure proper selection and fit are addressed.  To qualify as safety eyewear, all prescription safety glasses will have met the CSA Standard CAN/CSA-Z94.3-92 or , in some cases, the U.S. ANSI Standard Z87.1. If they meet the standard, you should be able to find “Z87” on the temple pieces. This mark confirms that the frame meets ANSI Standard Z87.1 and is stronger than standard street-wear frames, and thus prevents the lenses from being pushed into your eyes. The top outside edge of the lenses will have the manufacturer’s logo moulded or etched. Prescription safety eyewear needs to have side shields permanently mounted and affixed to the frame. And, safety prescription eyewear is available with single vision, bi-focals and even progressive lenses.

We need to continue to work hard at ensuring our eye safety programming is successful at protecting workers. Fully developing a program consistent with provincial and territorial OHS regulations  and following CSA Z94.3.1Guideline for selection, use, and care of eye and face protectors is an important first step. Ensuring that only compliant  equipment is being used is critical to the success of this programming, too. Finally, employee education and training are needed to help employees understand not only when to wear safety eyewear and how to wear it, but also why 100% user compliance is required if we are going to eliminate eye injuries.  Eyesafe can assist with all these tasks, allowing the company safety officer to focus on tasks other than administration.

Glyn Jones is a partner at EHS Partnerships Ltd. in Calgary.  He is a consulting occupational health and safety professional with 30 years of experience. He is a regular safety conference speaker in Canada, and he provides program design and instructional support to the University of New Brunswick’s OHS certificate and diploma programs.

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