- ChE 352 Chemical Process Safety Homework (4 of 6) Variation on 3-21: A drum contains 42 gal of acetone. If the lid of the drum is left open (lid diameter = 3 ft), determine the time required to evaporate all the toluene in the drum. The temperature is 90°F. Estimate the concentration of acetone (in ppm) near the drum if the local ventilation rate is 1000 ft³/min. The pressure is 1 atm. How does the concentration compare with the TLV-TWA?