Welding fume is dust with particles below 1 micrometre that bypasses natural barriers and reaches the alveoli. Stainless steel adds hexavalent chromium classified as carcinogenic, galvanised material adds zinc oxide causing metal fume fever, and paint coatings add organic vapours. Each of these needs a different filter.
The order is always the same: ventilation and extraction at source first, personal protection second. A mask does not replace extraction, because it protects only the person wearing it, and only when it seals properly.
Match the filter to the hazard. For welding fume alone class P3 is enough, for work on painted surfaces and with degreasers you need a combined A2P3 filter, and for coated materials check the safety data sheet. A gas filter has a limited service life once opened, so write the date of first use on the housing.
A powered air system with a belt mounted unit is the most comfortable answer for full day work. It feeds filtered air under the helmet, creates a slight positive pressure and cools the face, so the welder does not lift the helmet for air. Check the unit output and the battery run time for one shift.
With facial hair, half mask fitting stops working. In that case the only effective answer is positive pressure equipment, that is a helmet or hood with powered air.