Eyewear is fast becoming a part of fashion, and this includes safety glasses. Employees are now even wearing dark tint safety eyewear indoors, and the rainbow of coloured lens available is adding to the popularity. The seemingly endless options in terms of lens colour and coatings makes it difficult to reconcile safety features of the different tints and colours from fashion.
Understanding light exposure and work environments is important in choosing the right lens colour and tint to optimize performance and wearer comfort. Visible light is what we refer to as white light and it is the range of the electromagnetic spectrum easily detectable by the eye. Infrared light (IR) is at the low frequency, or red, end of the visible spectrum and ultraviolet light (UV) is at the high frequency, or purple, end of the visible spectrum. Too much white light can impact vision and IR and UV can be harmful to the eyes. The lens tint and lens colour of safety eyewear can help to optimize performance, provide better visibility and clarity, and increase wearer comfort. Both the lens tint and lens colour can impact glare, the recognition of colour variations and contrast. The selection of the right lens for your safety eyewear can be helpful to control these exposures. Finding the right choice requires a little analysis and perhaps some trial and error.
Lens Colours & Tints
The available lens colours is extensive, with colours ranging across the visible spectrum from red to blue. Grey lenses are the most common colour for general outdoor use. The grey colour allows for the most accurate colour visibility and the available range of tints allows for use in most applications. The range of grey tints runs from very light that lets in most of the light to quite dark that absorbs more light.
Generally, tinted and coloured lens are not necessary for most indoor work locations. Too much tint or a coloured lens that alters depth perception and contrast can create a safety issue for the wearer. Outdoors grey tinted lens are usually the best choice, but a coloured lens may be appropriate.
The specialty lens colours typically found in safety eyewear are listed below with a short description:
- Amber or yellow lenses block the blue end of the light spectrum and greatly improve contrast in low light. These would be good to wear in low light when the work being completed requires detail.
- Dark amber (sometimes seen as copper-coloured or even brown) lens block blue light and glare, and allow improved visual contrast.
- Green lenses are less common, but are associated with preserving colour balance and providing a slight improvement in contrast.
- Dark orange lenses increase contrast. Such a lens might be used when doing indoor inspections that require detail.
- Red lenses increase depth perception and allow for better detail recognition.
- Blue lenses reduce the yellow glare associated with sodium vapour lighting as might be found in some large older warehouse operations.
Unless there is a specific circumstance requiring a coloured lens, the preferred choice is a grey lens with a tint appropriate for the work conditions. Lens tints are measured by the amount of light they absorb or block. A high tint means a large percentage of the incident light is absorbed by the lens. The choices of lens tints ranges from clear to very dark. Standard sunglasses have light tint of around 50-80%. A high altitude mountaineer might use a lens with a dark tint of 90-95%. Although there will be some variation in the description of a lens and the associated lens tints here is a general guide:
15-20% tint: Near-clear lenses are good for very lowlight or night-time conditions.
30-50% tint: Light coloured lenses are good for low-light or overcast outdoor conditions.
50-80 % tint: Typical sunglass lens tint that is good for all-purpose use.
81-95% tint: Dark lens tint is good for very bright, very sunny conditions.
When it comes to safety eyewear and lens colour selection, welding is a special case. The wavelengths of the light created by welding operations can be narrower and the brightness of the light course is very high. The light radiation from welding can severely and permanently injure the eyes. The lens in a welding helmet must be a specific shade number to protect against the light radiation associated with welding. Specialized equipment is available to protect against welding hazards and only this specialized equipment is to be used when welding.
Polarized & Transition Lenses
In addition to these many lens shades and colours, the CSA Standard Z94.3.2020 Selection, Use and Care of Protective Eyewear lists polarized lens and photochromic lens as available options for use in safety eyewear.
- Polarized lenses dampen out the glare of reflected light that may cause eye fatigue. Glare from light reflected off water or snow and ice is most common. This dampening effect can be a great advantage unless of course there is a need to be able to reconcile these reflected surfaces allowing you see them more specifically.
- Transition or photo-greying lens automatically darken as natural lighting levels increase. The lens reacts to the UV light in sunlight. The benefit of this lens type is that you don’t have to change glasses when going from indoors to outdoors. The disadvantage is the lens take a minute to change making things very bright when you first go outdoors into the sun and very dark when you first return indoors. Transition lenses may not be the best choice for all safety eyewear applications.
Mirrored lenses are popular for recreational use, but are not specifically listed for use in safety eyewear.
Choosing the right lens colour for your safety eyewear requires you properly assess the workplace hazards and experiment with different tints. Ensure any product you choose is CSA compliant and remember – eyewear needs to be worn to protect the eyes. Being an advocate for consistent use and being a coach to support compliance with safety eyewear use is important to worker eye safety.
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.