This European standard specifies the scale numbers and transmittance requirements for filters intended to protect operators performing work involving welding, braze-welding, arc gouging and plasma jet cutting. The other applicable requirements for these types of filters are given in EN 166:1995. Guidance on the selection and use of these filters are given in Annex A. The specifications for welding filters with switchable luminous transmittance and welding filters with dual luminous transmittance are given in EN 379:1994.