Fogging has been an issue for workers ever since safety eye wear has been worn, but it has become a more prominent issue during the pandemic with mask wearing. If you are one of the millions wearing glasses and having to mask up because of COVID you have also likely experienced fogged lenses. Not only does it make it harder to see, but it can also be significant enough to create a real hazard for glasses wearers. So how do we reduce fogging?
Lens fogging is caused by tiny water droplets that form condensation on the surface of lenses. It happens anytime there is a temperature difference between your glasses and the outside environment. Whenever you walk into a warm area after being in a cooler area you should expect this condensation effect. The same thing is happening when you wear a surgical mask as part of the COVID-19 protocol, and the warm exhaled breath escapes up the top of your mask. When the warm exhaled breath hits the lenses of your glasses or safety eyewear it results in fogging.
The Science Behind Fogging
The science of lens fogging is interesting. The surface of your glasses are potholed with microscopic depressions. Moisture is attracted to these uneven areas and can easily condense forming a microdroplet. Dirt and grime on your lenses have the same effect creating a place for the moisture to condense. Scratched or dirty lenses fog up faster and more heavily than newer, unscratched, and clean lenses.
Scuba divers have a good understanding of this phenomenon. Before donning their masks and diving in scuba divers will regularly spit saliva into their masks to give the inside of the lens a good rinse. The saliva creates a moisture film on the inside of the lens and decreases the surface tension, preventing fogging. The saliva acts as a surfactant and this decreases the surface tension of the droplets such that they can’t form as easily. The water from the condensation does not mound up as tiny fog beads or droplets but instead breaks to form bigger droplets that just roll away from the surface of the mask.
There are a few different products available on the market that can temporarily prevent foggy glasses. These include anti-fog sprays, wipes and coatings designed to reduce the condensation of moisture on lenses. All anti-fog techniques involve applying a very thin, very smooth coating over the lens that fills the microscopic depressions, reduces the surface tension of the lens, which reduces micro-droplet formation. Anti-fog sprays and wipes have to be re-applied regularly to work best because regular handling and cleaning will remove the surface coating re-exposing the microscopic depressions that encourage fogging. Anti-fog lens treatments are a more permanent solution than wipes.
Anti-fog coatings can be applied to plastic, polycarbonate, and other eyeglass lenses, including high-index lenses and photochromic lenses. The coating is applied to the lenses before they are machined to the exact sized needed to fit the frames. Some coatings are also effective in reducing glare. Some anti-fog coated lenses require a special lens cloth to wipe the lenses, which also works to improve the anti-fog performance of the coating. The lens coating in conjunction with the lens cloth can result in hours of fog-free performance.
Protecting Your Eyewear
In addition to using these anti-fog technologies the other things you can do to reduce lens fogging is to keep your lenses clean and scratch-free. Ensure you have a program in place to protect safety eyewear from damage. Employers can provide appropriate cleaning stations so employees can easily keep their safety eyewear clean. Proper frame selection will also help reduce fogging. Tight fitting frames may reduce air circulation, and this will increase moisture being trapped that will lead to condensation. In most circumstances the right frames for your face will ensure there is sufficient airflow to prevent condensation.
There are many types of safety eyewear available and there are many options for keeping them fog free. Making the right choice might seem overwhelming, but an Eyesafe™ optometrist can help. They will ensure you get the professional advice needed, plus you can book your annual eye exam to be certain vision impairment isn’t adding to the problem.
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.