We have a number of proccess's which require the use of small amounts of solvents such as MEK, Toluene, gunwash etc applied to our product by paint brush. These chemicals are dispensed and issued to operatives in small quantities for use over a 4 hour period. All tasks are undertaken using LEV but my question is, at the end of the shift, there may be a small amount of contaminated chemical left in the container, the small amount being no more than maybe between 20ml & 50ml. As the chemical is contaminated, we cant reuse or recycle it. Given its only a small quantity left, we tend to leave the pot under the LEV to evaporate. Comments please.

And the serious repsonse. The solvents you mention are very volatile, the quantties are small, so long as there's no fire risk I see no problem in leaving to evaporate. Most laboratories have a collection tank for waste sovent but if your quantities per week are less than a litre then evaporation seems ok. Paint sprayers evaporate that quantity every minute of the day!

JohnW, your not wrong about the residue, which hardens when the solvent has evaporated. Operatives tend to throw away the pots when the contaminant becomes excessive, which in itself is another issue I suppose. The figure you mentioned of a litre a week (we wouldn't collect that in a month), is this an arbitrary figure or documented somewhere?