Some Whitley Workstation users require additional safeguards to reduce the possibility of bacteria contained inside workstations being released via the main chamber exhaust valve and the airlock exhaust valve. To address this requirement our Whitley HEPA workstations can be specified with additional HEPA filters fitted to these exhaust valves. This particular option is specifically designed for the Whitley 85 and 95 chambers.
During laboratory tests, these filters were challenged with high concentrations of aerosolized bacteria. Based on the number of bacteria aerosolized inside the chamber, the volume of gas discharged through the valves and the number of colonies recovered outside the workstation immediately adjacent to the exhaust valve, we were able to calculate that there was a reduction in bacterial numbers of greater than 99.999% compared with the number of bacteria that would have been released in the absence of such filtration.
The full results of the laboratory tests have been written up as Technical Note HE08: HEPA filtration of gas discharged from Whitley workstations: bacteriological testing. It is important to emphasise that Whitley Workstations are not safety cabinets.