This shows a vehicle spraybooth with a fully extracted floor (ie the extraction goes from sidewall-to-sidewall rather than having an extracted ‘pit'). With a fully extracted floor, recirculating eddy currents around the sidewalls are largely eliminated. The video shows a small amount of smoke from a professional smoke machine being injected into the booth with the extraction running. The smoke machine is then removed from view and switched off.
The smoke is a good representation of how paint mist moves and clears in a spraybooth. Much of the cloud of smoke is extracted through the floor quite quickly but smoke also moves up to light fillets at the top of the booth (between the vertical wall and horizontal roof). The smoke slowly circulates in the area around the light fillet and gently ‘rains down' onto the area below (where a sprayer would be normally be operating) for tens of seconds. This clips helps to explain how even the best spraybooths can have areas that clear more slowly and why every spraybooth and spray room has a clearance time (during which operators must be protected by air-fed breathing apparatus).