Excursus Capacity of Protective Filters

Filter devices to protect against hazardous and/or lethal gases and vapors are divided a) into types according to the kind of gas to be filtered and b) into classes according to their capacity. Filters of class 3 with a large capacity are stored externally, usually in a container to be carried at one s side, since they are too heavy to be carried on the mask. They are connected to the mask with a hose. Filters of class 2 are screwed into the mask and form the majority of all used filter types. Filters of class 1 are plug-in filters. 

Short-term excess up to twice of the table value is permissible 

485 Hauptverband der gewerblichen Berufsgenossenschaften, Atemschutz-Merkblatt, Carl Heymanns Verlag, Cologne Oct. 1981. 

Needless to say that the Deutsche Institut fur Normung (DIN, German Institute for Standardization) has determined the minimum values of break-through times of filters under standard testing conditions. These conditions are  

In Table 15 the values of different filter types are given with their respective harmful gas. 

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