From the environmental viewpoint, two essential areas of dust separation are distinguished; keeping the atmosphere free of dust, and keeping dust out of the air breathed by the workers in shops, factories, and other places. In connection with atmospheric dust removal, fundamental statements were made in the article 'Dust removal and combustion' in this journal (3/73) with the determination that only on the broadest international plane can real air purity be guaranteed and that for this purpose, appropriate warning and reading devices must be employed on just as broad a basis. The document covers monitoring of the air, industrial dust, air conditioning equipment, garbage burning, and bio-detergents.