One in 10 of people who get asthma from isocyanates in bodyshops is not a sprayer. This means they are getting exposed some other way. One of those ways is entering a spraybooth/spray room before all of the fine, invisible mist has cleared. Even the most efficient booths take over a minute to clear after spraying has finished. Some take significantly longer. A spray room can take up to half and hour to clear.
Anyone entering a spray booth or spray room needs to know what the clearance time is (see appendix 2 in HSL/2006/43 - 'Review of commercially available party fog machines suitable for determining the clearance time of paint spray booths and rooms').