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Executive introduction
Healthcare ventilation sits where several pressures on the estate meet. Engineering services are taking a growing share of capital budgets and floor area, the push for lower-carbon buildings adds another constraint, and airborne infection remains a daily operational risk. How air is supplied, directed and maintained now shapes cost, carbon and patient safety at once.
At Trovex’s September 2026 conference, three engineers set out how the sector might respond: Jerry Slann, chartered engineer and director of authorising engineers at IOM World, and Blanca Beato Arribas and Andy Vernon of Hoare Lea. This article draws out their arguments: why the direction of airflow can matter as much as its volume, why a system’s real test begins at handover, and what it would take to design for clean air rather than simply more air.
Directing air, not just moving it
Most ward ventilation is judged by how much air it delivers. Jerry Slann, drawing on 51 years in engineering and around 30 in healthcare, argued that where the air goes matters as much. A clean airflow path supplies air at the foot of the bed and extracts it at low level behind or beside the bed head. Air passes the clinician and the patient’s breathing zone before it can reach the corridor.
The principle is not new. It is already standard in recovery bays, in maternity suites to control nitrous oxide exposure, and in neonatal intensive care to manage the risk of a nitric oxide leak. The question he put to the sector is why it stops there.
His evidence came from one refurbished bedded ward, comparing three outbreaks before and three after clean airflow paths were introduced.
Outbreak | Before: ward closure (days) | Before: confirmed cases | After: ward closure (days) | After: confirmed cases |
|---|---|---|---|---|
1 | 97 | 33 | 12 | 18 (9 staff, 9 patients) |
2 | 52 | 15 | 21 | 16 (3 staff, 13 patients) |
3 | 40 | 25 | 5 | 3 (3 patients, 0 staff) |
Figures as presented by the speaker. Across the three outbreaks, closure days fell from 189 to 38.
This is a single-ward comparison rather than a controlled trial, but the scale of the change is hard to ignore. Slann framed the choice in patient terms: would you prefer a better-looking room, or to “go home two weeks earlier because you haven’t got an infection?”
He was equally direct on cost. Ducting an extract down to bed level adds little when it is specified at design stage; it is redrawing the design after the fact that gets expensive. The research base is also growing: Slann is a co-investigator on a £3 million NIHR-funded project with University College London, developing an AI tool to find the best placement for HEPA filters in consulting and examination rooms.
Where design meets daily use
If clean airflow paths show what good design can achieve, Blanca Beato Arribas focused on how easily it can be lost. In her view, a ventilation system’s real performance is decided after handover: in how it is built, maintained and used.
The design targets themselves are well founded. Isolation rooms are typically designed to 10 air changes an hour and a 10 pascal pressure differential, with up to 35 pascals in theatres, figures grounded in CFD modelling, physical testing and peer-reviewed evidence. The problem is what happens next. Trades leave rooms full of penetrations, so they can never hold pressure. False ceilings conceal years of leakage. As she put it, such ceilings are “sometimes used to hide all sorts of crimes, from dust to holes.”
Use matters too. Blocked grilles, propped-open doors and patients opening windows to feel less isolated can each undo a sound design. Unused sinks bring legionella and pseudomonas risk, and grilles obstructed by bins, trolleys or furniture stop working as intended.
She argued that almost all of this can be designed out if it is considered before handover:
Specify solid ceilings and defined airtightness, so rooms can be pressurised and stay that way.
Plan plant around maintenance. One air handling unit serving six isolation rooms means a filter change takes all six out of use.
Design for flexibility. A positive pressure ventilated lobby (PPVL) isolation room can switch between infectious and immunocompromised patients; a negative-pressure-only room designed a decade ago cannot.
The rising cost of more air
Andy Vernon challenged an assumption that runs through healthcare ventilation: that more outside air is automatically safer air. After roughly 30 years in construction and engineering, he asked a deliberately simple question: “Are we genuinely designing for air, or for clean air?”
The cost of the current approach is visible in the numbers he presented. MEP costs on healthcare projects have risen from around £850 per square metre a decade ago to over £3,500 per square metre on New Hospital Programme schemes. The share of a hospital given over to plant has grown from roughly 14–16% to as much as 27–33%. On this trajectory, he suggested, engineering services costs will soon outweigh the cost of the building itself.
The physical consequences follow. An air handling unit around six metres cube no longer fits a five-metre plant room, so the same performance now needs three smaller units instead of two, taking further space from clinical use. Every square metre of plant is a square metre not available for patients.
From air volume to verified clean air
Vernon’s answer was not to lower standards but to change what is measured. Set against the 20-year horizon of the New Hospital Programme, he outlined a pathway in four stages:
Smarter, demand-based sensing that responds to how spaces are actually used.
Recirculation supported by UV and HEPA filtration.
Hospitals that tune their own airflow by occupancy through a live digital twin.
The prize, in his view, is smaller, lower-cost, lower-carbon buildings that keep their safety standards. The condition is governance: any move towards recirculation happens with infection prevention and control teams and authorising engineers signing off each step, not bypassed by it.
The three arguments connect. Slann shows that directing air well can outperform simply supplying more of it. Beato Arribas shows that performance depends on decisions made long before occupation. Vernon shows why the sector can no longer afford to treat air volume as a proxy for safety.
Key takeaways
Direction matters as much as volume. Clean airflow paths, supplied at the foot of the bed and extracted low at the bed head, are already proven in recovery, maternity and neonatal settings. General wards are the next step.
The evidence is building. On one refurbished ward, outbreak closures fell from up to 97 days to as few as 5.
Design-stage decisions are the cheap ones. Low-level extract, solid ceilings and defined airtightness cost little when specified early and a great deal when retrofitted.
Plan plant for maintenance, not just capacity. Shared air handling units turn routine filter changes into multi-room closures.
Flexibility protects future value. PPVL isolation rooms can serve both infectious and immunocompromised patients.
More air is becoming unaffordable. With MEP costs above £3,500 per m² and plant taking up to a third of floor area on some schemes, volume alone is no longer a sustainable route to safety.
Change needs governance. Any move towards recirculation and smart control must be led with infection prevention and control teams and authorising engineers.
Looking ahead
The direction of travel is from supplying air to proving it is clean. For estates leaders and design teams, that means treating airflow direction as a design parameter on general wards, writing operability and maintenance into the brief, and building the monitoring that will let future hospitals tune ventilation to real occupancy. Questions raised by the audience show where the debate goes next: if the evidence for clean airflow paths is this strong, should it become a minimum requirement in guidance? And how will trusts integrate new approaches with legacy systems without creating a two-tier estate? Neither has a simple answer, but both will shape briefs on new and refurbished hospitals over the coming decade.
Continue the conversation
Trovex will continue to bring together engineers, clinicians, estates teams and designers to explore how healthcare environments can be made safer and more resilient. Join us at our next event as the conversation continues, and share your own experience of designing and operating healthcare ventilation.
To see Trovex’s hygienic healthcare ventilation units, visit the Hygipod Vent page.
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