This video clip is shot inside an average spray room where the extraction is via a wall mounted axial fan. A black backcloth has been erected and two high-intensity parallel-beam lights have been set up behind and to the left and right of an HSE Inspector. The one illuminates the area around the inspector and the other illuminates the area near the fan. The video is played back at high speed because otherwise nothing much seems to happen. The Inspector injects a cloud of smoke from a professional smoke machine. The smoke spreads quickly through the spray room but then appears to just hang in the air. The camera zooms in on the fan and some movement of smoke can be detected.
Paint mist in the air moves in the same way as the smoke - almost randomly in most of the room with directional flow only visible by the extraction fan and next to any inlet. The levels of isocyanate in spray rooms have been measured at levels up to 300 times the workplace exposure limit and may take up to half an hour to clear of paint mist.