In occupational health and safety and when working with hazardous substances, terms like smoke, dust, “E” dust or “A” dust are often mentioned. These terms are clearly defined in the statutory provisions and Technical Rules for Hazardous Substances. The difference between smoke and dust and the reason dust is harmful to the lungs are summarized below.


According to the Technical Rules for Hazardous Substances 900 (Technische Regeln für Gefahrstoffe – TRGS 900), both dust and smoke are very finely dispersed solid particles in the air. Dust is generated by mechanical processes or swirl-ups, smoke includes formation by thermal and/or chemical processes.

“E” and “A” dust fractions are two components of dust, defined in the Ordinance on Hazardous Substances (Gefahrstoffverordnung), Annex I, Part 2, 2.2. The “E” dust fraction is the proportion of dust that can be inhaled. The “A” dust fraction is the proportion of the inhalable dust fraction that can reach the pulmonary alveoli and bronchi. Dusts can lead to permanent lung damage when overburdening the lung, even if the solid particle does not present a health hazard in itself.

The general dust threshold limit value (Allgemeiner Staubgrenzwert – ASGW) relates to the “E” and “A” dust fractions.

General dust threshold limit value

The Occupational Exposure Limit Value (OELV) for inhalable dust fractions (“E”) is 10 mg/m³. For respirable dust fractions (“A”), the OELV is 1.25 mg/m³ at an average density of 2.5 g/cm³. In contrast to “E” dust fractions, the TRGS 900 recommends converting OELVs on the basis of the material density.

According to the TRGS 900, the general dust threshold limit value includes poorly soluble or insoluble dusts without specific regulations. Lacquer aerosols, coarsely dispersed particle fractions and dusts created with nanomaterials are excluded from this definition. The general dust threshold limit value does not account for substance-specific properties that may be subject to more stringent occupational exposure limit values.


Sources: H.F.Bender, Sicherer Umgang mit Gefahrstoffen, WILEY-VHC, 2011, ISBN: 978-3-527-32927-4

Ordinance on Hazardous Substances (Gefahrstoffverordnung – GefStoffV), consolidated version, as of 03/02/2015

Technical Rules for Hazardous Substances 900 (TRGS 900), as of 29/06/2015