WELDING FILTER LENSES

A few posts ago we talked about welding helmets and how they protect from welding sparks, spatter and radiant heat. But we left protecting the eyes from a welding arc’s harmful radiation for a separate post. Electric arc welding emits IR/UV radiation and intense visible light. Unprotected from these hazards, both eye damage and discomfort can occur. The PPE for protecting welder’s eyes is filter plates and lenses installed in welding helmets. (Traditionally, the 2” X 4 ¼” rectangles used in welding helmets were called “filter plates” and the 50 MM circles used in goggles were called “filter lenses”. But with the advent of auto darkening, both are generally called “filter lenses” today.)

A filter lens serves two purposes. The first is to diminish the intensity of visible light to a point where there is no glare and the welding area can be clearly seen. The second is to block harmful infrared and ultra-violet radiation coming from the arc. Filter lenses come in a variety of shades which are designated by a number. Many people mistakenly think that the lens shade number corresponds to the amount of protection that is provided to the eyes and the higher the number, the better the protection. Actually, the shade number indicates the degree of visible light provided. The lower the number the lighter the shade; the higher the number the darker the shade.

 All filter lenses block 100% of IR/UV regardless of shade number. The filter lens shade number selected depends on the type of work and somewhat on the preference of the welder. Consequently, the filter lens shade number selected must not vary more than two shades from the numbers recommended. A welding filter lens shade should only be selected by a trained welding safety official.

OSHA 29 CFR 1910.133- Eye and face protection, ANSI-Z49-1, and the American Welding Society each publishes a recommended filter shade chart similar to the one below.

Virtually all passive filter lenses are made from polycarbonate. The top quality lenses are injection molded. Molding assures consistency of shading throughout the lens. Avoid filter lenses stamped from sheet stock. Most passive filter lenses cause a welder to see his work in various shades of green. But there are specialty gold plated filter lenses that not only reflect radiant heat and lower the temperature inside a welding helmet, but also allow a welder to see his work in natural colors. They are a good investment in safety and productivity

Always install a clear plastic “cover” plate over top of the filter lens to protect the filter from sparks, spatter and getting scratched. If the welding helmet has a lift-front filter holder, always install an impact resistant, clear, polycarbonate safety lens behind the filter in the body portion of the lens holder as a last line of protection when the filter lens holder lid is lifted. Some welders even install a safety plate behind the filter in helmets with stationary filter holders if there is space to do so.

 Remember to always wear approved protective spectacles under a welding helmet at all times. They are your primary eye protection. Welding helmets are classified as secondary eye protection.

 Like all PPE, there are differences in quality among filter lens brands. Most welding helmets come from the factory with a filter lens installed and you are better off staying with that same supplier’s brand of replacement filter lens. In general, the top brands of welding helmets can be relied on to provide the best quality filter, safety and cover plates and lenses.


And make sure any filter lens you consider meets the test for transmission of radiant energy prescribed in  ANSI/ISEA Z87.1-2010, Practice for Occupational and Educational Eye and Face Protection.


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KTF disclaims liability for any injury of any nature whatsoever, whether indirect, consequential or compensatory, directly or indirectly resulting from the use of or reliance on this blog post. KTF also makes no guaranty or warranty as to the accuracy or completeness of any information published herein. The selection of any PPE should only be made by responsible safety officials.