Different FFP2 masks use different filter materials. On the one hand, the filtration effect is related to the particle size, and is also affected by whether the particles contain oil or not. FFP2 masks are usually classified according to filtration efficiency and whether they are suitable for filtering oily particles. Oil free particles such as dust, water-based fog, paint fog, oil-free smoke (welding smoke), microorganisms, etc“ Although the filter materials of "non oily particles" are common, they are not suitable for oily particles, such as oil mist, oil fume, asphalt fume, coke oven fume, etc. The filter material suitable for oily particles can also be used for non oily particles.