DRAINAGE SYSTEMS


Lewis Turner, which started to explore infection risk using computational fluid dynamics (CFD) mathematical modelling to investigate pathogen airflow characteristics – clearly a topic very much connected with the COVID-19 pandemic.


The Trelawny Scanning Suite and Haematology & Oncology Ward at the Royal Cornwall Hospital in Truro, with the unit’s MRI scanner shown, inset.


future refurbishments and new builds in Cornwall.” There has been a long-term trend in the


NHS to remove WC covers on sanitary appliances to facilitate seating for persons with disabilities. While this was temporarily suspended during COVID-19, it has started to be reversed as the pandemic recedes, with the spotlight once again returning to patient physical safety at the expense of infection control measures associated with infection propagation from WCs. Perhaps we don’t need to change


patient behaviour – just transition to less traditional thinking about infection control; closing the WC cover just takes the problem out of plain sight. Perhaps there is a case for updating Health Technical Memorandum (HTM 04- 01) with the addition of risk-assessed best practice guidance on the provision and operation of WCs, particularly in settings housing augmented care patients. The June 2023 CIBSE Journal contained


a report by Tim Dwyer titled ‘Hospital ventilation’ based on a student paper by


High-speed image study This, together with the recent high-speed image study released by the University of Boulder in Colorado in the US,1


offers a


window into the less publicised world of infection control associated with the earlier SARS and present COVID infections, where WC bioplume generation could provide a transfer mechanism. The high- speed photography method gives a very graphic illustration of possible bioplume infection propagation resulting from the flush action of a standard ‘wash-down’ WC (see Figure 1). Recent research work, including that carried out by Loughborough University in collaboration with Otter Vacuum,


Figure 1.


Left: photographs of the commercial toilet (1.6 gallon/6 litres per flush) and illuminated aerosol plume at t= 2.8, 4.4, and 6.4 seconds (University of Boulder, Colorado, USA1


).


Bottom left: (A) Image of the illuminated plume at t = 6.4 seconds after WC flush initiation. (B) Enlarged image of the region denoted by the red box in part A, post-processed to increase exposure and decrease contrast. This renders dimmer light from smaller particles visible, and demonstrates that the smaller particles (green glow) are well predicted by the locations of larger particles (imaged as discrete points of light). Also visible in the lower left are several large droplets that are following ballistic trajectories, and are outside the aerosol plume envelope.


NOTE: Each operation of a vacuum toilet extracts everything from the bowl and around 50 litres of air, including odours and the potentially harmful bioaerosols..., just at the time when infection transfer is highest.


68 Health Estate Journal October 2023


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