OSHA, in a letter of interpretation (05/13/1982 — The use of photochromic lenses in industry), prohibits the use of photochromic lenses for safety glasses at inside work locations which have variable lighting conditions, because the variable tint lenses would cause temporary vision impairment when the light changes from bright to dim or vice versa in the work area.
However, they are allowed inside when the lighting conditions do not change substantially and the employees constantly stay in one area, particularly if glare or bright lights are a problem. They may also be used by employees working outdoors, provided there is no ultraviolet or infrared hazard.