How to reduce fogging on prescription safety eyewear

By Glyn Jones

Note: In accordance with CSA Z94.3 – 2015, anti-fog coatings are not approved in Alberta. However, Eyesafe™ has special approval to provide this coating, as we have tested it to meet impact standards. As of January 2024, Eyesafe is the only safety eyewear distributor in Alberta approved to provide anti-fog coatings.

 

A major complaint of employees wearing safety eyewear, including prescription safety eyewear, is the issue of fogging. When a worker is working hard and sweating, their safety eyewear can fog up.  Additionally, moving in and out of buildings or work environments at different ambient temperatures and different humidities can contribute to fogging. Fogging is not only a major annoyance for workers — it also poses a significant safety hazard, making it a crucial concern when choosing safety eyewear.

 

Safety eyewear fogs up when water from the air—for example from sweat, breath, or ambient humidity—condenses on the surface of the lens. The condensed water forms tiny droplets across the surface of the lenses, scattering light and making it hard for the wearer to see clearly. This happens when there are changes in temperature, humidity, or even the physical activity of the wearer.

 

Fogging occurs when warm moist air, such as exhaled breath, comes into contact with a cooler surface. For example, when you enter a heated building from outdoors on a cold day, moisture in the indoor air will condense on the relatively cool safety glasses lens. Similarly, when you leave an air-conditioned area and walk outside into a hot humid environment, moisture in the air outside will condense on the relatively cool lens. The fog stays on the lens until the temperature and humidity on the lens come into balance with the surrounding air. In simpler terms, your glasses stay foggy until their surface temperature matches the air temperature.

When your prescription safety eyewear fogs up, your initial reaction might be to take them off and wipe the lenses on your sleeve. While this may solve the problem temporarily, it is not the best solution and there are a few reasons why you need to find a better way to deal with fogging.

• Your shirt may not be clean and dust or dirt on it can scratch the lenses.
• Taking your safety eyewear off to wipe the lenses takes you off task and is a distraction that could expose you to a worksite hazard—after all, if you are wearing safety eyewear there are likely eye safety hazards in your workplace and without your safety eyewear in place you may be at risk of an eye injury.
• If your safety eyewear is prescription taking your glasses off to wipe them creates a temporary period where you can’t see what’s going on.
• Wiping fogged lenses isn’t the best solution. There are better and more permanent ways to manage safety eyewear fogging.

All anti-fog techniques work by changing the surface of the lenses in two ways: 1) by using a surfactant to decrease the surface tension of condensing water, or 2) by using a hydrophilic material to create a more water-friendly environment. When surfactants are used, the lower surface tension prevents the condensed water from forming large droplets that scatter the light and cause fogging. Instead, condensed water spreads out evenly across the lens, preventing the refraction of light associated with fogging. In the case of hydrophilic materials, they act like a sponge, soaking up the water as it condenses but releasing it to the edges of the lens. This means that fogging may occur briefly but is quickly cleared from the field of view.

Three ways to prevent fogging

Some anti-fogging solutions are better than others, and most lenses will fog if the humidity is high enough, but all are much better than standard, untreated lenses. Here are three things you can do to more effectively prevent safety eyewear fogging:

1. Keep your glasses clean

Before using putting your safety eyewear, you should clean it – every time. Clean lenses do not fog as readily as dirty lenses. To clean your safety eyewear, use a cleaning solution designed for safety eyewear, or a mild detergent like dish soap. Many people use dish soap as a common “home remedy” for fog-proofing glasses. Cleaning your lenses leaves a fine film of cleaning solution on the lenses, which inhibits water droplet formation reducing the likelihood of fogging. If time allows, let the glasses air dry after cleaning.  If you’re in a hurry, dry them with soft, low-lint cloth.

2. Anti-fog spray, anti-fog gels, and anti-fog wipes

There are various anti-fog solutions available, such as sprays, anti-fog gels, and anti-fog wipes. These aim to create a thin film on the surface of the lens, preventing the formation of water droplets. Anti-fog sprays and gels typically contain either a surfactant or a hydrophilic solution that are applied to the surface of the lens. Both sprays and gels are applied and then wiped off, leaving behind a see-through film. Anti-fog wipes come as single-use packages or as microfibre cloths pre-coated with the surfactant or hydrophilic solution. Like the sprays and gels, they leave behind a thin, see-through film of surfactant or hydrophilic solution.

It’s important to note that these treatments won’t stay in place permanently, and repeated applications are required to maintain the anti-fog effect. Most sprays, gels, and wipes will need to be reapplied at some point over the life of the glasses. Even the longest-lasting sprays typically only around a month, with most only lasting about 24 hours. For compatibility and to avoid damage, it is best to buy the anti-fog product recommended by the safety eyewear manufacturer.

3. Anti-fog lens coatings*

Anti-fog lens coatings take advantage of today’s advances in lens coating technology. The surface coating acts much like the hydrophilic solution, preventing the water droplets from forming. Instead, the moisture will flatten out across the lens, preventing refraction and allowing the wearer to see through the lenses more clearly. The coatings also add a degree of scratch resistance to the lenses.  The coating may either be permanently sealed on the lens or integrated into the plastic.

*In accordance with CSA Z94.3 – 2015, anti-fog coatings are not approved in Alberta. However, Eyesafe™ has special approval to provide this coating, as we have tested it to meet impact standards.

 

Lens fogging remains a common problem for many workers who wear prescription safety eyewear. There are ways to prevent it and by understanding the causes of lens fogging you can find an optimal solution for your circumstance. By following these guidelines and using the prevention methods discussed, you can keep your lenses clear and your vision sharp.

 

Glyn Jones is a partner at EHS Partnerships Ltd. in Calgary. He is a consulting occupational health and safety professional with 35 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.