Sources: (face)
Standards: DIN 4844-2, EG 92/58/EG

Note: for working in a dusty environment without hazardous gases, a dust mask is often sufficient. Please refer to the appropriate icon.

Gas filters are filled with a filtering medium that binds th polluting substances from the air either physically or chemically. Typically, activated carbon is used.

The active part of a gas filter could be percieved as a lot of fine layers. The contaminated air flows perpendicularly through these layers from the environment to the inside of the mask. The contaminated air will first saturate the outer carbon layer. The deeper the air flows, the less contaminants will be found in the air. The saturated layer is also called dead layer, while the partially saturated layers are called the active front. As more polluted air is purified the active front gradually shrinks. When the last layers become saturated, the harmful substances can also accumulate on the outside. If this starts to happen, it is a signal that the filter is saturated. Such a saturation does not happen suddenly, and the concentration of pollutant in the mask will only reach the concentration in the ambient air gradually. It goes without saying that with more hazardous substances, a wider margin of safety should be taken.


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