Page 20 - OHS, April 2021

PPE: VISION PROTECTION
What You Need to Know About Anti-Fog Safety Glasses
Anti-fog measures are a critical part in keeping safety glasses safe.
BY KATHERINE FAULK
Foggy lenses are something most glasses wearers have dealt with in the last year during the COVID-19 pandemic. Those who have always needed PPE for their jobs have been dealing with this issue for even longer. Fogging
eyewear is a huge inconvenience and safety risk to those workers. In fact, fogging lenses are the number one reason workers remove or do not wear safety eyewear. Luckily, there is a solution in the form of anti-fog safety glasses. Before we dive into the science of anti-fog, it is important to understand the cause of fog itself.
What Causes Fogging?
Fogging lenses can be caused by several factors. Regardless of its cause, fog is the result of water vapor that has condensed into fine droplets and collected on the lens. This is typically because the lens is cooler than the air around it. Why would this be? There are several potential reasons:
Humidity. An abundance of warm, moist air is one of the most common causes of eyewear fog. Whether working outdoors or in purposefully humid environments, warm air will collide with the cooler eyewear and cause it to fog.
Temperature change. Drastic changes in temperature are another common cause of fogging lenses. Going from a cold location such as a refrigerated unit or even just an air-conditioned indoor location to a warmer one will cause air to condense.
Body heat. People working in warm environments or those exerting a large amount of physical force might also have to deal with fogging lenses due to their body increasing the temperature of the air around them. Sweat may also drop on eyewear and be treated similarly to fog.
Face coverings. Some face coverings—especially when improperly worn—cause warm breath to go up into the orbital cavity. This has become increasingly more common as people wear masks to protect themselves from COVID-19.
While not a direct cause, washing anti-fog safety glasses can also increase fog risk, as water and soap can rub off some anti- fog coatings. For that reason, it is always important to follow manufacturers’ instructions for proper care of anti-fog safety glasses. Every manufacturer will have different rules on how to clean their lenses based on the type of anti-fog used as well as the material the eyewear is made of. Following these guidelines is the best way to maintain the integrity and longevity of your anti-fog eyewear.
History of Anti-fog Technology
Like so many scientific innovations, anti-fog safety glasses have NASA to thank for their invention. In the 1960s, NASA was worried that astronauts would be put at risk due to fogging visors when exploring space. During a spacewalk, Astronaut Eugene A. Cernan tested their newly invented anti-fog technology and found that his helmet visor fogged in reaction to the atmosphere, except for where an anti-fog solution had been applied.
From there, anti-fog technology was developed and became available in many forms such as sprays, gels, wipes and coatings
applied during the manufacturing process. The latter solution is considered one of the most effective and long term today.
The Science of Anti-Fog Safety Glasses
The latest anti-fog technology manipulates moisture on the surface of the lens through lens-coating agents. There are several types of products that can be used for this, such as surfactants, detergents, polymers, hydrogels, colloids and nanoparticles. Currently, there are two major categories of these coatings: hydrophobic and hydrophilic. While both are effective at managing fog, they have different functions.
Hydrophobic means “water fearing.” This type of coating repels water causing it to run off the lens. It is best for high moisture environments and those where workers are regularly transitioning between environments with varying temperatures.
Hydrophilic means “water loving.” With this type, water is absorbed by the coating. Eyewear featuring this anti-fog is best for moderate moisture environments. Both coating types can adequately serve various anti-fog needs.
Coatings are added to anti-fog safety glasses in a variety of ways, most commonly through dip and flow processes. The decades-old dip process enables agents to adhere to both sides of the lens as they are dipped in the coating. On the other hand, the flow process coats one side at a time, which allows for different agents to be cured on each side if desired. Other methods for lens-coating include spray and spin processes, which are rarely used for anti-fog safety glasses.
Anti-Fog Safety Standards
Until 2020, there was no U.S. safety standard for anti-fog safety glasses. This meant that any manufacturer could claim to have a high-quality anti-fog product with no way to measure its effectiveness and longevity. While Europe does have a safety standard for anti-fog safety glasses (EN166) this standard only states that glasses must specify which coatings are applied and contains test protocols. Longevity is not addressed by that standard.
Last year, the International Safety Equipment Association (ISEA) created a U.S. standard (ANSI Z87.1-2020) for anti-fog safety glasses. The standard mandates that eyewear can only be classified and marked as anti-fog if lenses remain fog-free for at least eight seconds. Having an ANSI standard means that U.S. workers and safety coordinators can purchase anti-fog safety glasses knowing that they are getting a quality, tested product. Approved eyewear will be designated by an “X” on the lens.
The Cost of Fogging Lenses
Any risk management officer or safety coordinator can see the potential problems fogging lenses pose. As mentioned, it is the top reason for safety eyewear to be removed or not worn at all. In many of these work environments, safety glasses aren’t just smart to wear, but mandated by OSHA or other regulatory bodies. Not wearing safety equipment can put the company at risk financially and the worker at risk both physically and financially.
16 Occupational Health & Safety | APRIL 2021
www.ohsonline.com