Fogged-up eyewear

Responding is Jimmy Wong, global head, eye and face protection advanced technical service engineer, 3M, St. Paul, MN.

There are many reasons eyewear lenses can fog up. Working with a fogged lens can be frustrating and dangerous, and removing eyewear to wipe away fog can expose eyes to potentially dangerous workplace impact hazards and debris.

For workers in metalworking, oil and gas, construction, and other physically demanding environments, safety eyewear is designed to try to keep lenses clear of fog – even when workers are in hot and humid conditions or climate-controlled areas. For example, in the food industry when machinery and equipment must be washed down, a high amount of moisture is in the air and eyewear can easily fog up – getting in the way of safety and productivity.

When assessing how to reduce fogging when wearing safety eyewear, environmental, health and safety professionals should first review how the hazard can be engineered out. Dehumidifiers or other environmental controls such as temperature regulation can help maintain steady levels of heat and humidity, which can help keep lenses more clear. Providing a comfortable work environment will reduce perspiration, a natural way the human body cools itself.

However, if the environmental conditions are outside of EHS control, certain personal protective equipment can leverage anti-fog technologies and help reduce eyewear fogging.

Traditional anti-fog technology comes in two forms: hydrophobic and hydrophilic. Hydrophobic coatings are typically found on car windshields and cause the water to bead more easily, allowing the water to gain mass and roll off. This is less common for eyewear and faceshields due to the close proximity to the face.

In contrast, hydrophilic coatings are used to reduce the surface tension – typically using surfactants – allowing the water to create a continuous film on the lens. This is often preferable because light can then pass through water with minimal distortion, unlike droplets found in fogging.

Hydrophilic anti-fog coatings can help reduce fogging, but the technology has limitations. Hydrophilic, or having a strong affinity for water, means the coating can be dissolved by water. As you continue to use it, the effectiveness of anti-fog properties lessens and eventually stops working. To regain anti-fog properties, users can reapply coating using anti-fog sprays or wipes, which require additional cost and time.

Another limitation is oversaturation of coating due to poor airflow to the lens. Anti-fog coatings are not designed to “remove” water that causes fogging, but instead manipulate it so that it allows the user to see clearly. If there is not enough air to draw water off the lens, the film can become so thick that the coating can no longer control it, potentially causing distortion. As a result, it is a recommended best practice to balance gap coverage and airflow. If the task requires indirect or no venting, taking frequent breaks or using a full-face powered air purifying respirator are some options.

Today, PPE is available that incorporates premium anti-fog technologies that are bonded directly into the surface, and retains its hydrophilic properties for a longer duration of time so there is no need to reapply. By using safety eyewear with anti-fog technologies incorporated, workers can see clearly for longer, helping them stay safe and productive in most environmental conditions.

Editor's note: This article represents the independent views of the author and should not be construed as a National Safety Council endorsement.