INFECTION CONTROL The final word goes to Tim Fletcher: “I’m
grateful for the help and advice of Frank, Gordon, Barry, and the Midtherm UV team in this project. The success of the system has opened up more opportunities within our Trust than I had before. “I’m confident now 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’s proof of sound investment at lower capital and operating cost, as well as lower maintenance costs. “Going forward, I’m also excited about
Shown, left to right, are: Application engineer, Gordon Hurst, Frank Mills, Barry Paterson, director, Midtherm UV, and Richard Andrews, MD at Midtherm.
UV-C lamps use hardly anything.” The RAP is a dynamic situation. Patients
are constantly arriving and leaving this assessment area throughout the day, bringing in pathogens, so the Trust would never achieve a 100% reduction. Initially, we at Midtherm UV loaned the Trust four 250m3
sanitiser units, which recycle 1,000m3
/h mobile UV-C air /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. i.e. 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, and Influenza A.
Air tests at each stage 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 148 cfu/m3
to 46 cfu /m3 after the mobile
UV-C units were deployed. There was a 29.4% reduction in fungal levels. This was an expected result compared with 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 the inline duct unit, there was an 82% reduction in bacterial levels from an average of 385 cfu/m3
to 71 cfu/m3 . 66 Health Estate Journal October 2022
Individually designed Each unit is designed individually to meet site requirements. It’s far more cost-effective than multiple air-handling systems, because we’re also utilising the existing air-handling system, which gives economies of scale without any additional fan power. Otherwise, you’d use more, larger motors requiring increased power consumption, resulting in higher capital and running costs. Adding UV-C lamps to an existing air- handling system is a very cost-effective way of sanitising the air. These systems increase the cleansing effect, while avoiding energy losses and helping the NHS towards its net carbon zero targets - unlike increasing existing ventilation systems. Each solution is a combination of the intensity of UV-C radiation, and the time the air spends within the radiation zone, which determines the level of dose that is administered. Our systems are designed to kill Influenza A by administering an LD99
dose. Most other
viruses require a lower dose than this. Bacteria, in general, require four times the level of dose compared to viruses. Therefore, if you are killing the bacteria in the air, you will inactivate the viruses. If spores are the problem, we would then add more light in, or slow the air supply down.
Designing the system to kill particular pathogens You give us the pathogen problem, and we’ll design the system that will kill it. Since the guidelines and standards for UV-C were introduced, we’ve had a high level of interest, and orders placed for mobile units from Trusts and other healthcare providers across the UK. Midtherm UV offers a special purchasing
structure which allows all healthcare providers to benefit from the economics of air sanitisation by sharing in the total buying power across the NHS.
Barry Paterson
Barry Paterson is a director of Midtherm UV, a West Midlands manufacturer of UV-C air sanitisation products, based in Dudley. He and fellow director, Richard Andrews, have been working closely with the NHS to design effective, robust, UV-C air sanitisation solutions for mobile and fixed in-duct applications. Barry Paterson is a member of the IMechE COVID Task Force, which was involved with NHS estates engineers in compiling the new Guidelines & Standards for the Application of Ultraviolet (UVC) Devices for Air Cleaning in Occupied Healthcare Spaces.
working with NHS Estates on developing this further and embedding it into best practice. Considering the future uses of modular buildings in the NHS, this scheme, particularly technically, has been an excellent project and outcome. “I’m now 100% confident that in
installing a UV-C system we could capture all airborne bacteria and viruses within the confines of the area for the benefit of patient outcomes and staff safety, thereby aiding the reduction of HCAIs (hospital-acquired infections) and airborne transmission of infectious diseases, such as COVID-19, while at the same time saving energy and reducing our carbon footprint. Also, there is less risk to maintenance staff, as there are no HEPA filters to change.”
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