A pioneering trial at Maidstone Hospital has demonstrated the impressive effectiveness of UV-C ventilation against bacteria and viruses in a clinical setting, together with the technology’s ability to enable significant energy-savings.
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’. This has led to a demand for UV-C solutions by hospital trusts and other healthcare providers around the UK, particularly with the increased focus on airborne transmission of infection due to COVID-19.
Already widely used in healthcare settings in the USA and some European countries, the sanitising effect of short-wavelength light in killing bacteria and inactivating viruses was discovered in 1878.
Tasked with transforming an office and staff room into a seven-bay RAP (Rapid Access Point) for incoming ambulance patients, Tim Fletcher, mechanical project engineer at Maidstone and Tunbridge Wells Hospitals NHS Trust, explains: “In 2019, I was tasked with converting the rapid access point area into a seven-bay assessment unit. As part of the programme we had to look at installing a ventilation system, where one did not exist, other than natural ventilation from fenestration.
“The ceiling voids were very low due to 60% of the area having a flat roof and 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 install and suited the RAP’s layout. We were going down that route when airborne bacterial and viral transmission became more prominent and a particular issue due to COVID-19.”
Tim says: “As we neared the end of the project, we went into the March 2020 lockdown and it became apparent that we needed to do additional work on the system as it is a return air heat recovery system – taking existing air within the area and recycling it back into the room, with the introduction of fresh air.”
The inline duct mounted UV-C unit located above one the RAP unit’s seven bedded bays
Tim Fletcher was introduced to Frank Mills, an accomplished ventilation expert and chartered professional engineer and founder member of the Institute of Mechanical Engineers COVID-19 Task Force, led to the addition of UV-C to the system.
Frank 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.
Tim explains: “After discussing the type of system required with Frank and Gordon, it led me to being introduced to Barry Paterson, of MidthermUV. The trust engaged a trial with MidthermUV’s mobile UV-C filtration units as part of an NHS trial, with the agreement of Professor Tony Fisher, who was keen to see how the units performed in a clinical setting.”
An independent company undertook air sampling in the already busy RAP prior to the UV-C mobiles being deployed. Tim Fletcher was concerned at the contaminate levels of the initial tests. “MidthermUV loaned four mobile UV-C filtration units, each capable of sanitising 250m3/h of air,” says Tim. “These were located around the RAP unit. Similar airborne testing was undertaken to establish the efficiency of using a UV-C filtration system in the area and other suitable clinical locations in the hospital.
“The tests showed a significant 69% reduction in CFUs (colony forming units). The technology presented significant improvements in reducing CFU’s and immediately demonstrated that UV-C filtration offered an attractive future option for NHS ventilation sanitisation.”
Tim says: “Following the results, working with Frank, Gordon and the Midtherm team we decided to develop a duct-mounted UV-C filtration system that was added to our ventilation arrangements in the RAP unit. This unit was accommodated in the pitched roof ceiling void at one end of the area.” MidthermUV were so confident in the system that they undertook the work on a sale or return basis.
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.
“After a week further air sampling was undertaken. The CFU results were further improved. An overall 82% reduction in bacterial levels had been attained.”
100% of existing air within the RAP is subject to UV-C functional filtration. The results were more effective than the mobile units were achieving. Potential exists for UV-C units in new installations, instead of large ventilation systems with high energy loss due to single-pass 100% fresh air provision. This lower energy solution with lower space requirements is an advantage over traditional single-pass ventilation systems.
Quantum, the contractor is a distributor and installer of high velocity ventilation systems. This system proved easy to install supplying air conditioning to the RAP via 22 air nozzles. The air distribution in the RAP space assists in sanitising contaminated air via UV-C filtration.
Maintenance is low cost. The 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. With limited training, the maintenance team will change the lamps after 12-months. The manufacturer, Philips’s lamps have a minimum 9,000-hour life expectancy. A visual indicator in the RAP unit informs staff that the UV-C is functional.
The UV-C ventilation system offers benefits to hospitals in numerous clinical settings and it is likely that UV-C technology will gain popularity in both mobile air ventilation systems and duct mounted ventilation systems in the UK.
Tim says: “I can see a lot of benefits in this hospital, typically in waiting areas where the standards under which the area was constructed may go as far back as 1983, as they will do for many other hospitals across the country. I’m confident that we’ll see UV-C technology being rolled out, both mobile units and duct-mounted solutions, across the country.”
One of the four MidthermUV mobile air sanitising units during the trial
From a clinical and patient-focussed perspective, Joanne Green, the trust’s deputy director of infection prevention and nurse consultant for infection, says: “We are delighted to be part of this UV-C research project. Protecting our patients and staff from infection has always been our priority, which has become even more pertinent during the COVID-19 pandemic.”
Anna McNeela, emergency department matron at Maidstone Hospital, adds: “The UV-C results have been very impressive in our RAP’s area. The staff feel very comfortable knowing their working environment is being protect by UV-C filtration technology, especially against COVID-19 and other airborne contaminants.”
Well known by many hospital engineers, Frank Mills, amongst his many achievements is a past chair of CIBSE healthcare group and a member of the Royal Academy of Engineering task force on infection healthcare environments. Frank says: “It’s important to have a good mix of air flow – re-circulating air, and clean air – with fresh air. The solution at Maidstone Hospital is not full fresh air as in HTM 03-01 (Specialised ventilation in healthcare buildings) however it offers an effective solution in CFU count reductions in air ventilation systems.
“HTM 03-01 was first published in 1995 and 55% of UK hospitals were built before that time. Due to this many UK hospitals do not comply unless they have undertaken refurbishment work to these current criteria standards.
“As a consulting engineer, I work with many healthcare projects where it is found that there is not much ventilation.
“Many people assume that effective filtration in a system will render efficient air filtration. As a principle, if it is possible to reduce the viral load many assume this will be satisfactory in reducing airborne contamination. In hospitals the number of air changes per hour is a minimum of ten. This varies depending on the area concerned and increases in clinical areas with critical air quality requirements.
“UV-C has had an application in ventilation for many years. UV-C is effective as it destroys airborne viremia. 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.
“At Maidstone we managed to give them what they wanted. It’s an application that other hospitals might like to consider, particularly in light of COVID and our understanding of airborne pathogens.”
Frank adds: “There’s a lot of kit out there that’s nowhere near the standard required and not sustainable. We want to nurture a market of UK and European manufacturers who can produce a quality, sustainable product at the right price.
“It’s standard practice not to re-circulate air. However, the trust was already considering the task of decarbonisation when COVID introduced new dimensions into ventilation systems. The solution we’ve come up with here is a great step forward for the trust in achieving their target.
“It’s a pioneering project developed in conjunction with Tim Fletcher, who I must also give due acknowledgement to for the work he’s done on developing the scheme.”
Developing Midtherm’s UV-C system at the time was applications engineer Gordon Hurst, who says: “I applaud Tim for the way he’s dealt with this. If you treat the viral load, you’ll achieve a reduction. The best position to install the RAP’s UV-C unit was in the return air flexible duct connected high velocity air conditioning unit.
“The NHS can’t ignore this. The energy savings can be significant. 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. The UV-C lamps use hardly anything.”
Gordon Hurst, applications engineer, left; Frank Mills, NHS ventilation consultant; Barry Paterson, director MidthermUV, and Richard Andrews, managing director Midtherm
Barry Paterson, director MidthermUV, explains: “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 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 Klebsilla and inactivate all viruses likely to be encountered within a healthcare environment, including COVID-19, RSV, Norovirus, Influenza A.”
Barry says: “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 to 46cfu/m3 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.
“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, whilst avoiding energy losses and help the NHS towards its net carbon zero targets – unlike increasing existing ventilation systems.
“Each solution is a combination of 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, requires 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.
“You give us the pathogen problem and we’ll design the system that will kill it,” adds Barry. “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.”
MidthermUV 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.
The final word goes to Tim, who adds: “I’m grateful for the help and advice of Frank, Gordon, Barry and the MidthermUV team in this project. The success of the system has opened up more opportunities within our trust than I had before.
MidthermUV’s in-duct air sanitising unit alongside one of the mobile units
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 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.”
For further information, call MidthermUV on 01384 454 645, email [email protected] or visit www.midthermuv.co.uk
