EN 170:2002 Personal eye protection - Ultraviolet filters - Transmittance requirements and recommended use

 This European Standard specifies the scale numbers and transmittance requirements for filters that protect against ultraviolet (UV) radiation. Other applicable requirements for these types of filters, along with the frames and mountings to which these filters are affixed, are available in EN 166. Guidance concerning the selection and use of these filters is available in Annex B.

Note: the protective filters that serve as examples in this standard are not suitable for the direct viewing of bright light (e.g., from sources such as Xenon high-pressure arc lamps) nor are they suitable for the direct and indirect observation of an electric welding arc. 

The numbering table for filters and the reference for marking oculars and frames are available in EN 166.