Corridor care is increasingly being used across the NHS as hospitals manage sustained capacity pressures, raising important questions about environmental and airborne infection risk in non-clinical spaces. Here, Barry Paterson, Chartered Engineer and founder of Germicidal UV Ltd (GUV), draws on ventilation standards, outbreak evidence, and practical healthcare experience to explore how clean air delivery and supplementary air cleaning can help mitigate shared air risk, and argues that airborne infection control in corridor care is not optional, but a systems-based environmental challenge that must be addressed alongside clinical practice.
Across the NHS, corridor care has become a visible consequence of sustained capacity pressures. Patients are increasingly treated in corridors, waiting areas and other non-clinical spaces when emergency departments and wards exceed capacity.
The CQC has issued guidance to inspectors regarding care delivered in non-clinical spaces, reinforcing that corridor care must not become normalised and that trusts are expected to mitigate associated risks.¹ This creates a regulatory expectation: when non-standard spaces are used for care, environmental and infection risks must be assessed and managed.
Infection prevention is often debated in binaries: droplet or airborne, masks or ventilation, procedures or environment. The reality is far less dramatic, and far more practical. In healthcare, infection prevention works as a layered system:
- Strong policies and training.
- Disciplined clinical technique (hand hygiene, aseptic practice).
- Appropriate PPE.
- Environmental controls like ventilation and air cleaning.
No single layer is enough on its own. Ventilation cannot compensate for poor procedural practice. PPE cannot fix weak environmental controls. Policies mean nothing without consistent application. Each layer reduces risk. Together, they create resilience.
In my work, I operate within the environmental layer, focusing on shared air risk. However, this approach is only effective when aligned with robust IPC practice across the board.
Infection prevention is not about choosing one solution — it is about building systems where the layers reinforce each other.
Airborne transmission and ventilation: what the evidence shows
Respiratory infection transmission is influenced by multiple environmental and behavioural factors, including:
- Ventilation rate.
- Airflow patterns.
- Occupancy density.
- Duration of exposure.
The relationship between ventilation and infection probability is well established in airborne infection modelling, including the Wells—Riley equation.²
The WHO recognises the importance of ventilation in reducing airborne transmission of respiratory pathogens and has issued technical guidance emphasising both air changes and air cleaning.3,4
The core principle is straightforward: increasing clean air delivery (through ventilation or air cleaning) reduces the concentration of infectious particles in shared air.
Hospital ventilation systems are typically designed around enclosed rooms and defined airflow pathways. Corridors operate differently.
Research into airflow dynamics in healthcare environments demonstrates that door opening and staff movement can drive air exchange between rooms and corridors, allowing air (and potentially contaminants) to move across boundaries.5
When corridors are used for patient care:
- Occupancy density increases.
- Exposure duration increases.
- Multiple aerosol sources may be present.
- Air mixing between clinical and non-clinical zones increases.
Shared air exposure is recognised in infection control guidance. For example, CDC measles guidance defines exposure as being in the same airspace as an infectious individual, including for a defined period after that individual has left.6
This demonstrates that in certain infections, shared air alone can constitute meaningful exposure.
Evidence from high-density healthcare settings
Outbreak investigations across multiple pathogens demonstrate that indoor crowding and ventilation influence transmission dynamics.
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Influenza
Ventilation and crowding have been identified as contributing factors in the spread of influenza in indoor environments.7
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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
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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:
- High-density waiting areas.
- Temporary overflow spaces.
- Shared transitional zones.
- 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’.
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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.
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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.
The strength of the UVC in the zone is relatively low, typically 30—50 µW/cm². The dose delivered is a combination of UVC intensity and time. In these types of devices, airborne pathogens, due to thermal buoyancy effects, remain in the UVC zone for a relatively long period of time, typically >30 s. This results in a typical reduction in the airborne bio-burden of > 60 per cent.
Again, additive effects are achieved through the buoyant air movements. These types of devices are particularly useful in corridor applications.
During installation, the level of UVC radiation in the occupied zone beneath the UVC field must be measured using a calibrated UVC meter. The safe UVC LEL is 60 J/m².
This equates to a UVC power level of 0.2 µW/cm² . Responsible installers should check this UVC level is not exceeded when measured at a height of 1.8 m above floor level.
Their low power consumption results in low running costs, typically around 50p per day, combined with a very low carbon footprint.
Regulatory expectation and risk mitigation
The CQC expects providers to:
- Assess environmental risk.
- Mitigate patient safety concerns.
- Avoid normalising corridor care.
Infection prevention must therefore extend to any space used for patient care, even if originally designed for circulation rather than treatment.
When corridor care occurs, trusts should be able to demonstrate:
- Ventilation assessment.
- Occupancy management.
- Environmental risk mitigation.
- Proportionate infection control measures.
Conclusions
1) UVC is a well-established option for reducing airborne infection risks. It is easily installed into existing healthcare settings and provides immediate results.
2) Preventing just one case of HAI can save the NHS significantly more than the cost of a single UVC air cleaner and its operational costs over five years. This does not account for the additional knock-on effects of patient segregation, cancelled procedures, increased waiting lists, and staff absenteeism.
3) Corridor care is fundamentally a capacity challenge. Airborne infection risk within corridor care is an environmental systems challenge.
4) Evidence from ventilation science, airborne infection modelling, and outbreak investigations consistently demonstrates:
- Airborne pathogen concentration increases in shared indoor air.
- Higher clean air delivery rates reduce infection probability.
- Airflow disruption and density amplify risk.
5) When care moves into corridors, ventilation and air cleaning strategies must move with it.
6) Addressing airborne infection risk in non-clinical spaces is not merely best practice — it is increasingly a regulatory expectation.
Barry Paterson
Paterson Barry Paterson Bsc (hons) C Eng. MIMechE MASHREA is a Chartered Engineer and founder of Germicidal UV Ltd (GUV), a UK-based manufacturer of UVC air cleaning equipment. He has played a leading role in establishing UK manufacturing of in-house UVC designs developed in accordance with ASHRAE and IEC standards. Hundreds of his UVC units are installed across NHS healthcare settings.
Barry contributed to NHS guidance on the application of ultraviolet devices for air cleaning in occupied healthcare spaces. His work focuses on the engineering application of UVC and ventilation strategies to reduce airborne infection risk in healthcare environments.
References
1 Care Quality Commission. New guidance for inspectors on care in non-clinical spaces [Internet]. London: CQC; 2024 [cited 2026 Feb 25]. Available from: https://www.cqc.org.uk/news/new-guidance-inspectors-care-non-clinical-spaces
2 Wells WF. Airborne contagion and air hygiene. Cambridge (MA): Harvard University Press; 1955. Available from: https://en.wikipedia.org/wiki/Wells-Riley_model
3 World Health Organization. Roadmap to improve and ensure good indoor ventilation in the context of COVID-19 [Internet]. Geneva: WHO; 2021 [cited 2026 Feb 25]. Available from: https://www.who.int/publications/i/item/9789240021280
4 World Health Organization. Global technical consultation report on proposed terminology for pathogens that transmit through the air [Internet]. Geneva: WHO; 2024 [cited 2026 Feb 25]. Available from: https://cdn.who.int/media/docs/default-source/documents/emergencies/global-technical-consultation-report-on-proposed-terminology-for-pathogens-that-transmit-through-the-air.pdf
5 Tang JW, Nicolle AD, Pantelic J, Koh GCK, de Wang L, Amin M, et al. Door-opening motion can potentially lead to a transient breakdown in negative-pressure isolation conditions. Build Environ. 2013;59:463—471. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC7114940
6 Centers for Disease Control and Prevention. Measles infection control in healthcare settings [Internet]. Atlanta: CDC; [cited 2026 Feb 25]. Available from: https://www.cdc.gov/infection-control/hcp/measles/index.html
7 Luongo JC, Fennelly KP, Keen JA, Zhai ZJ, Jones BW, Miller SL. Role of mechanical ventilation in the airborne transmission of infectious agents in buildings. Indoor Air. 2016;26(5):666—678. Available from: https://pubmed.ncbi.nlm.nih.gov/26562748
8 Bonifait L, Charlebois R, Vimont A, Turgeon N, Veillette M, Longtin Y, et al. Detection and quantification of airborne norovirus during outbreaks in healthcare facilities. Clin Infect Dis. 2015;61(3):299—304. Available from: https://pubmed.ncbi.nlm.nih.gov/25900175
9 Centers for Disease Control and Prevention. Guidelines for environmental infection control in healthcare facilities [Internet]. Atlanta: CDC; [cited 2026 Feb 25]. Available from: https://www.cdc.gov/infection-control/media/pdfs/guideline-environmental-h.pdf
10 NHS England. Health Technical Memorandum 03-01: Specialised ventilation for healthcare premises — Part A [Internet]. London: NHS England; 2021 [cited 2026 Feb 25]. Available from: https://www.england.nhs.uk/wp-content/uploads/2021/05/HTM0301-PartA-accessible-F6.pdf
11 HM Government. The Building Regulations 2010: Approved Document F — Ventilation. London: The Stationery Office; 2021.
12 Centers for Disease Control and Prevention. Upper-room ultraviolet germicidal irradiation (UVGI) [Internet]. Atlanta: CDC; [cited 2026 Feb 25]. Available from: https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation/uvgi.html