INF ECTION P R EVENTION
The results
Air tests were carried out at each stage – pre-installation, following deployment of the mobile UV-C air sanitiser units, and following on the inline duct installation. The initial results indicated a 69% reduction in bacterial levels from 148cfu/m3 m3
to 46cfu/
after the mobile UV-C units were deployed. There was a 29.4% reduction in fungal levels. This was an expected result compared to the reduction in bacterial levels, due to the irradiance dosages required to inactivate fungal cells and yeasts being around four times higher than the dosage required for bacteria. Following the installation of inline duct unit there was an 82% reduction in bacterial levels from an average of 385cfu/m3
to 71cfu/m3 .
“The technology presented significant improvements in reducing CFUs and immediately demonstrated that UV-C filtration offered an attractive future option for NHS ventilation sanitisation. “Following the results, we decided to add a duct-mounted UV-C filtration system to our ventilation arrangements in the RAP unit. This unit was accommodated in the pitched roof ceiling void at one end of the area,” commented Fletcher. Working with Quantum Group, the installer of the high velocity air conditioning system, the system was designed in accordance with NHS UV-C guidance and installed in the return air ductwork. The installation was completed within a day, while the RAP remained fully functional – with the exception of the one bay, where the work was carried out.
Anna McNeela, emergency department matron at Maidstone Hospital, commented: “The UV-C results have been very impressive in our RAP area. The staff feel
One of the four MidthermUV mobile air sanitising units during the trial
very comfortable knowing their working environment is being protect by UV-C filtration technology, especially against COVID-19 and other airborne contaminants.”
Energy and cost savings In addition to the infection prevention benefits, the lower energy solution with lower space requirements could offer an advantage over traditional single-pass ventilation systems.
Mills, a past chair of CIBSE healthcare group, advised: “One of the main benefits of UV-C applications is that they do not cause the substantial pressure drops in a ventilation system that filters do. This application also contributes to net zero carbon reduction and can eliminate a number of filters in the ventilation system… This is an application that other hospitals might like to consider, particularly in light of COVID and our understanding of airborne pathogens.” The Trust was already considering the task of decarbonisation when COVID introduced new demands for ventilation systems. The solution developed for the Maidstone and Tunbridge Wells Hospitals NHS Trust offers a step forward towards achieving the Trust’s sustainability targets. “The energy savings can be significant,” commented Hurst.” You can use nearly all your existing cooling load and reduce the viral load at the same time, with next to no additional power required – UV-C lamps use very little energy.”
The maintenance costs are also low – the
The inline duct mounted UV-C unit located above one the RAP unit’s seven- bedded bays
JUNE 2022
Trust’s estates team carries out inspections to check the UV-C is functioning and a visual check of build-up on filters. The UV-C lamps and filters are relatively inexpensive to renew. The Philips lamps have a minimum 9,000-hour life expectancy and a visual
Gordon Hurst, applications engineer, (left); Frank Mills, NHS ventilation consultant; Barry Paterson, director MidthermUV, and Richard Andrews, managing director Midtherm
indicator in the RAP unit informs staff that the UV-C is functional. With limited training, the maintenance team will change the lamps after 12-months.
Fletcher concluded that he is looking
forward to developing the system further and embedding it into best practice at the Trust. “This has been an excellent project and outcome,” he commented. “I’m confident that we can use this type of ventilation system across our Trust in existing ward and clinical areas that previously used natural ventilation by opening windows. It is a sound investment at lower capital and operating costs, as well as lower maintenance costs. “Most importantly, I am now confident we can capture airborne bacteria and viruses, within the confines of the area, for the benefit of patient outcomes and staff safety – thereby aiding the reduction of hospital-acquired infections and airborne transmission of infectious diseases, such as COVID-19.”
CSJ
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MidthermUV’s in-duct air sanitising unit alongside one of the mobile units
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