Evaluation of selected aerosol-control measures on flow sorters

Flow sorters produce microdroplets as part of their normal operation, and if these microdroplets escape into the room, they are potentially hazardous. We have tested several aerosol-control measures on a commercial flow sorter. To accomplish this, T-4 phages were introduced into the sorter's liquid jet through the sample injection tube, and culture plates containing lawns of T-4-sensitive Escherichia coli bacteria were exposed around the sorter for each operational configuration. After the exposure, the plates were incubated and then scored for plaques. A single phage-containing microdroplet landing on a plate was sufficient to cause a plaque of lysed bacteria to form. The number of plaques was thus an indicator of how much aerosol was released for each configuration. Aerosols were controlled most effectively by catching the central, undeflected stream in a vacuum-exhausted tube; this technique, coupled with the manufacturer's vacuum-exhaustion of the air around the sorting location, produced no plaques. Several failure modes were tested, including having the central stream hit the outside of the catch-tube or deflection plates, and loss the manufacturer's vacuum-exhaustion system. Many flow sorters allow the underflected stream to splash into a flask or beaker, an approach that produces the most plaques if instrument-failure modes are excluded. The simple addition of a catch-tube removed this major contributor to the aerosol production.