I need to do some work on WELS and its not my strong point.  We've done some air sampling for spraying using a product that uses TOULENE.

We sprayed for 3mins (realistic for the area covered) and took are samples for Toulene 3m away after the spray was finished and it read 100ppm, after 10mins it dropped to 20ppm, we didnt record any further after that.  The COSHH data sheets state the WEL is 100ppm and TWEL is 50ppm.

So is it a case that after 10 mins the fumes drop below 20ppm and so is considered that RPE isnt required? I'm trying to work out the safe level (and I know zero is safe !) when a room can be entered after spraying without RPE being worn.

thanks

Was an occupational hygienist advising and assisting you with this?

what we're being asked for by the client is "once painting has taken place, when can people use the room"? does that make more sense? the MSDS states the WEL's but I'm struggling to find anywhere how you work out a safe / background limit.  I've spent several days reading and searching but without a clear answer.  Yes we would like the room to be zero, but that isnt likely to occur for a few days due to settling.

We state that whilst spraying is taking place, anyone within 15m must wear RPE, this is because the PPM drops off to below the short term and long term PPM at 10m, so I've added another 5 for good measure, but I know the client will reject this as being unworkable as other trades need access to the area asap after spraying so want to know the estimated "clear" time.

I've not seen the deleted comments by others, but I do find some pick issues with questions for the sake of showing stature or awkwardness, I ignore.