The ability to make air flows visible via smoke in a wind tunnel also allows the depiction of pollutant dispersal. For this, smoke is blown into the tunnel at the pollutant sources (e.g. chimneys). The distribution of the smoke and its dilution in the study area becomes visible and can be documented by photograph (Fig. 4/10a und Fig. 4/10b) or videotaping. Direct results about the resultant concentrations are, however, not possible to measure at this juncture. This representation can nevertheless be very helpful – particularly for decision-makers – in demonstrating potential problems.

	Fig. 4/10a: Dispersal of pollutants in a wind tunnel, made visible by smoke, Source: IHW, Karlsruhe
	Fig. 4/10b: Flow past a multistoried building in the wind tunnel, made visible by smoke, Source: IHW, Karlsruhe