INF ECTION P R EVENTION
Tackling airborne transmission of pathogens
The pandemic has increased our focus and understanding of the importance of mitigating the risk of airborne transmission of infections in the hospital environment. With patient safety at the forefront, Maidstone Hospital recently trialled a UV-C ventilation system to deliver a significant reduction in CFUs.
Already widely used in healthcare settings in the US and some European countries, the sanitising effect of short-wavelength light in killing bacteria and inactivating viruses was first discovered in 1878. More recently, the benefits of UV-C were highlighted by Mike Ralph, chief engineer and senior policy/ strategy lead (hard FM) at NHSE&I – and others – in the final draft of ‘Guidelines and Standards for the Application of Ultraviolet (UVC) Devices for Air Cleaning in Occupied Healthcare Spaces’.
Along with an increasing focus on airborne transmission of infection, during the pandemic, this awareness has led to growing demand for UV-C solutions by hospital Trusts around the UK. Against this backdrop, Maidstone Hospital embarked on a pioneering trial of UV-C ventilation – successfully demonstrating the effectiveness of the technology against bacteria and viruses in a clinical setting, as well as the ability to deliver significant energy-savings.
Background Tim Fletcher, mechanical project engineer at Maidstone and Tunbridge Wells Hospitals NHS Trust, was tasked with transforming an office and staff room into a seven-bay rapid access point (RAP) area for incoming ambulance patients in 2019. “As part of the programme, we looked at installing a ventilation system, where one did not exist, other than natural ventilation from fenestration,” Fletcher explained. “The ceiling voids were very low due to 60% of the area having a flat roof – the limitations with a roof mounted system meant that we could not install a traditional ventilation system. “It was decided that a high velocity ventilation system, which allows smaller ductwork in the ceiling void, should be installed. I had previously used this type of solution successfully on other projects. The system functioned well, was good to
Tim Fletcher, Maidstone and Tunbridge Wells Hospitals NHS Trust
install and suited the RAP’s layout. We were already going down this route when airborne bacterial and viral transmission became a more prominent issue due to COVID-19.” As the hospital neared the end of the project, the UK went into the March 2020 lockdown. Fletcher was introduced to Frank Mills, an accomplished ventilation expert, chartered professional engineer and founder member of the Institute of Mechanical Engineers COVID-19 Task Force, which led to the addition of UV-C to the system. Mills was engaged with Mike Ralph, chief engineer NHSE&I, and Professor Tony Fisher, of Liverpool University, on establishing guidelines and standards for UV-C in the NHS; while another key figure in the industry, Gordon Hurst, had separately developed a ventilation UV-C filtration system.
The solution After discussing the type of system required with Mills and Hurst, the Trust engaged a trial with MidthermUV’s mobile UV-C
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filtration units, with the agreement of Professor Fisher, who was keen to see how the units performed in a clinical setting,” Fletcher explained. Barry Paterson, director MidthermUV, explained: “Initially MidthermUV loaned the Trust four 250m3
/h mobile UV-C air sanitiser units which recycles 1,000m3 /h.
The units were positioned centrally around the assessment area, which gave us four air changes per hour (ACH), in addition to the existing system’s fresh air flow of one ACH hour – an equivalent of five ACH. “Several weeks later, the permanent in-duct UV-C unit was installed into the return air duct of the RAP’s air conditioning unit. The UV-C unit was sized to handle 2,000m3
/h while administering a high
dose of UV-C radiation. It is sufficient to ensure at least a 2-log reduction LD99, 99% disinfection, to kill bacteria such as MRSA, E-coli, and Klebsiella and inactivate all viruses likely to be encountered within a healthcare environment, including COVID-19, RSV, Norovirus, Influenza A.”
JUNE 2022
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