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Positive pressure suits are widely used at BSL-4 to protect operators from contact with microbiological agents. As there is the potential for the outside of the suits to become contaminated during use, they must be decontaminated prior to final exit from the high-containment laboratory. Chemical showers are used to remove biological material from suits, and the shower effluent is collected for subsequent treatment by heat or chemicals. The efficacy of showering to clean/remove biological materials from two different BSL-4 suits (ILC Dover and Delta) was studied using Bacillus atrophaeus spores dried directly onto the suit surface as a surrogate contaminant, with a 4 log colony forming unit (cfu) reduction pass criterion required. Initial studies using water alone, without disinfectant, achieved a 1-2 log cfu reduction in the microbial contamination. However, direct scrubbing, using a lightweight brush combined with relatively short cycle times (6 minutes) and low water volumes (<45 L per cycle) achieved an average spore reduction of 3.4 log cfu from the suit. The log cfu reduction was dependent on suit type, position of the contamination on the suit surface, and suit fit. Higher reductions (mean 4.2 log cfu) were achieved with the ILC Dover suit than the Delta suit (mean 3.6 log cfu) when the tests were undertaken using experienced staff who had been matched to the suit size. The study highlights that assumptions cannot be made about the efficacy of shower decontamination systems for BSL-4 facilities and that familiarization with decontamination improves the efficacy of removal of biological material during showering. Materials and Methods This study measures the effectiveness of biological material removal not disinfection activity and so a resistant, non-pathogenic spore tracer was chosen. Ethics The initial study plan required the use of volunteers and hence the project was submitted to the UK NHS Na

Theoretical analysis of the condensation of hydrogen peroxide gas and water vapour as used in surface decontamination.

High Efficiency Particulate Air (HEPA) filters are required to minimize the release of microorganisms from laboratories and other settings. This study was carried out to assess whether a range of microorganisms captured on HEPA filters would survive under normal operating conditions. Bacillus atrophaeus (NCTC 10073), Staphylococcus epidermidis (NCIMB 12721), MS-2 coliphage, Escherichia coli (NCIMB 9481), Brevundimonas diminuta (NCIMB 11091), and Aspergillus brasiliensis (ATCC 16404) were individually aerosolized using a Collison nebulizer and captured on HEPA filter material. Clean air was drawn through the loaded filters for 6 days at a constant rate (face velocity of 0.4-0.5 m/s -1 ) for all organisms and for 210 days for B. atrophaeus to simulate the use of a HEPA filter. Pre-packed sterile filters were also contaminated with B. atrophaeus which survived on the HEPA filter material for 210 days with no significant loss of viability. MS-2 coliphage and A. brasiliensis survived over the 6 days with no significant loss of viability. There was a 5-log reduction in viability of S. epidermidis over 6 days, while both Gram-negative bacteria, E. coli and B. diminuta, were not recoverable after 48 hours of exposure. This study highlights the need for risk assessments and rigorous guidelines on the use and handling of air filtration membranes exposed to resistant pathogenic agents to minimize the risks of occupational exposure.