Just read Part 2 of an aticle on Welding safety in the October issue of Occupational Health & Safety. A portion of the article talks welding helmet lenses. According to the article "Determining the correct lens is greatly simplified by referring to the chart published by the American Welding Society". "You can obtain a copy of the AWS lens chart (Publication F2.2;2001) by phoning 1-800-443-WELD (9353)".