INFECTION CONTROL 100 100 75 75 50 50 25 25 0 0
0
contributing factors in the spread of influenza in indoor environments.7
n Norovirus Although norovirus is primarily transmitted via contact and surfaces, it can become aerosolised during vomiting events, and airborne virus particles have been detected in hospital outbreak settings.8
n General airborne infection risk Ventilation and/or air cleaning reduces airborne pathogen concentration and is a recognised infection control measure.9
Across pathogens, a consistent environmental pattern emerges: poor ventilation combined with high occupancy increases the risk of airborne transmission.
Ventilation standards in UK healthcare In England, healthcare ventilation design is guided by HTM 03-01.10 HTM 03-01 specifies ventilation performance standards for defined clinical areas. Corridors are not generally designed as treatment spaces, and ventilation provision may differ from that of enclosed clinical rooms. Within HTM 03-01 (2021), the use of new technologies is recognised (Clause 4.11) as long as there is sufficient evidence to support their use. HTM 03-01 also references Building Regulations Part F under Section 3.7, ‘Legal Requirements’.¹¹ Clause 1.37 states that ventilation systems recirculating
air between spaces should be able to operate in a mode that reduces airborne infection transmission risk, including: a) 100 per cent outdoor air operation. b) Incorporation of UVC (ultraviolet C) germicidal irradiation systems.
When corridors are repurposed for care delivery, ventilation performance should therefore be assessed relative to the intended clinical use.
Equivalent air changes and supplementary air cleaning When mechanical ventilation cannot be structurally upgraded, supplementary air-cleaning technologies can increase effective clean air delivery. This concept is commonly referred to as equivalent air changes per hour (eACH).
WHO and CDC guidance recognise air-cleaning
technologies, including upper-room GUV, as potential risk-reduction measures when appropriately applied.3,12 These approaches do not replace ventilation, but can supplement it, particularly in:
n High-density waiting areas. n Temporary overflow spaces. n Shared transitional zones. n Corridors.
What engineering solutions are available? The two main technologies are UVC and HEPA filtration. The latter has two main drawbacks: noise and consumable costs. UVC devices are quiet and have lower operational costs. The size of the dose being administered in the UVC reactor chamber is calculated to reduce the pathogen’s viability. This effect is normally referred to in terms of ‘log reductions’: 1 log reduction = 90 per cent reduction, 2 log = 99 per cent, 3 log = 99.9 per cent, and so on. To enable comparison, it is helpful to use a known
pathogen as a reference point. In our designs, we administer a sufficiently large dose of UVC each time the air passes through the chamber to achieve > 3 log reduction in Influenza A viruses. Each time the air is subjected to UVC, the effect is additive. After two passes, a 3 log reduction becomes a 6 log reduction; hence much larger reductions are achieved over time. This level of dose achieves a bigger effect upon many other pathogens. The two main types of UVC device are characterised as either ‘active’ or ‘passive’.
n Active These kinds of devices use a fan to recirculate the air in a room, passing it through a zone of high UVC intensity, enclosed within a chamber, where any pathogens in the air are subjected to a measured ‘dose’ of UVC irradiation. Experience gained from installing these kinds of devices in healthcare settings has identified two key features that are important to their adoption; low noise and being unobtrusive. This latter feature is particularly important in ward settings where floor space is always at a premium. A neat solution is to place the UVC air cleaner in the ceiling. This has the added advantage of being able to use the flat ceiling surface to promote good air distribution via the ‘Coanda effect’. This arrangement provides a very effective solution,
typically achieving >70 per cent reduction in airborne bio-burden, with low noise levels (<35 dBA) and no interference with ward activities.
n Passive These devices are silent and are located on walls, well above head height. They use naked UVC that is directed though a louvre arrangement generating a precise zone of UVC irradiation just below the ceiling.
September 2026 Health Estate Journal 61
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4 ACH (air changes per hour)
Above left: UVC device illustration.
Above: graph showing % infection risk against ACH rate.
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Infection risk (%)
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