Figure 1.

Principle of operation of the air-liquid interface cell exposure system (ALICE). Three phases can be distinguished: During phase 1, a dense cloud embedded in an air flow is introduced into the empty chamber (panel a). During phase 2, the continuously supplied cloud forms a vortex near the bottom of the chamber and fills the chamber from bottom to top, while depleted air is extracted from the top part of the chamber (panel b). During phase 3, the flow and hence the influx of the cloud is stopped and the cloud -filled chamber is gradually depleted due to single particle settling (panel c).