If you work in a modern purpose built spray booth with large quantities of filtered air flowing past it is easy to believe that all the overspray is instantly carried away leaving the air safe to breath as soon as spraying is finished. This is a dangerous misconception. In fact, spray booths typically take between one to five minutes to clear. During this time, it is essential that you keep wearing your air-fed mask and no unprotected person enters the booth.
Spray rooms are much cruder devices than booths and are much slower to clear (it can take half and hour or more). The levels of isocyanate in spray spaces have been measured at levels up to 300 times the workplace exposure limit. If you want to carry on using a spray room you need to make sure it works as safely and efficiently as possible.
Anyone using a spray booth or room needs to know what the clearance time is (see appendix 1 of Controlling isocyanate exposure in spray booths and spray rooms (WEB36)). Booths and spray rooms only work effectively if they are kept maintained.