Recent results of investigating the phenomenon of "Black Magic Dust"

The effect of suddenly appearing large-surface block deposits in living spa ces (phenomenon of "Black Magic Dust") which has been increasingly observed in recent years has been examined systematically in an extensive program o f measurements. Eight housings concerned were selected. In addition to chem ical analysis already applied in the past, particular emphasis was laid on the recording and characterization of airborne dust and on thermographic me asurements. For investigations, it is important to know if the phenomenon i s still "active" at the time of measurement or if it is already "inactive" As claimed in the past, the visible black surfaces are essentially caused b y (fine) dust particles. The presence of semi-volatile organic compounds (S VOC) on wall surface supports particle absorption. In this contexts a disti nction must be made between an "adhesive film effect" and an "airborne effe ct" (fogging). However, no final answer to the question if these effects ar e always required "as a first step" for creating these phenomena could be o btained. Time-resolved thermography provided proof for colder wall areas, t hermal bridges and especially the type of air-flow being the decisive facto rs starting this phenomenon. Besides, the intensity of block precipitations also depends on individual living behaviour No relation between the phenom enon and outside air influences and VOC emissions could be discerned, the s ome applies to the simultaneous occurrence with microbial indoor contaminat ions.