158. In a mine or an asbestos extraction plant, drilling, crushing, drying, dry rock storage, ore processing or asbestos processing must not cause asbestos fibres to be emitted into the atmosphere in excess of the limit of 2 fibres per cm3 of dry gas at reference conditions.
For the purposes of this section, only fibres at least 5 µm long with a length/width ratio of at least 3:1 are calculated.