The first sidearm flask functions as the vacuum trap and the second acts as the overflow back-up. These two flasks contain enough household bleach so that the final concentration of waste is 10% bleach when full. An in-line PTFE 0.2um filter is the last defense and prevents aerosols from entering the line. The flasks should be set in a plastic bucket or tray so that if they break, the spill is easily contained. This image is adapted from the Biosafety in Microbiological and Biomedical Laboratories.