How do I prevent fogging on safety glasses?

I value my eyesight too much to not wear safety glasses, goggles, or a face shield in the shop. But fogging on the lenses drives me to distraction, especially when wearing a dust mask. Do you have any recommendations for keeping the fog at bay?
—Mark Finnegan, Park City, Kan.

Depending on the severity of the fogging, Mark, your solution may be as simple as buying eyewear with an anti-fog lens coating. Or switching to eyewear that has greater venting, or goggles that move the lenses farther from your face, allowing for better air circulation. Using a fan to keep the air moving around you can also help.

If those practices don't provide relief, try applying an anti-fog treatment, like those below left. In our tests, they prevented fogging entirely. A number of home remedies also work, including applying soap or shaving cream, and then buffing the lenses clear with a soft cloth. (Never use an abrasive product such as a paper towel.) Windshield rain repellents work similarly. The old trick of rubbing a bit of saliva on the lenses can work in a pinch, though the effect can be fleeting.

It also helps to use a dust mask with an exhalation valve that channels breath straight outward, away from your face. If you still experience fogging, try the trick shown below.

Respirators with silicone face seals completely block exhaled breath from reaching your eyes, but they can prove uncomfortable to wear in combination with eyewear.

Fortunately, these solutions come with small price tags. But if you find these don't work for you, the ultimate solution costs a few hundred bucks. A power air shield incorporates a rechargeable-battery-powered fan that sends a continuous stream of filtered, fog-eliminating air across your face.