Lead or lag? Rethinking ventilation in the NHS

Back in 2000, I asked a simple but uncomfortable question: Do we lead, or do we lag? At that time, it was becoming clear that clinical ventilation systems across the NHS were not always performing as expected. Rooms that should have been safe were not consistently so. Systems that were assumed to be protective were, in practice, falling short.

The framing still matters today. To lead is to operate a closed-loop system, one that measures performance continuously and adjusts in real time. To lag is to rely on open-loop assumptions — designing, installing, and then intermittently checking, hoping that the system behaves as it should.

HTM 03.01, the key document guiding ventilation in healthcare premises, is undoubtedly well-written and important. Yet fundamentally it is guidance that lags. It relies on design assumptions and periodic validation.

In clinical practice, this would be unacceptable. In patient care, feedback and monitoring are non-negotiable. The environments patients rely on deserve the same standard.

Clinical analogy: Monitoring patients vs monitoring air

My perspective is shaped by a clinical background. In coronary care, the idea of treating a patient without proactive monitoring is inconceivable. When a patient’s
ST segment shifts or an arrhythmia develops, the system leads. Alerts sound, staff act, and lives are saved.

Now imagine the opposite. A post-myocardial infarction patient is prescribed the correct drugs and fluids, but their heart is not continuously monitored. No ECG, no telemetry, no chemistry checks. The patient deteriorates silently. By the time deterioration is visible, the chance to intervene may have passed.

This lagging approach would never be accepted for patient care. Yet it remains standard for the air that patients breathe and for the environments in which care is delivered. Ventilation systems are installed, validated, and then left to run on assumption. Problems are discovered only retrospectively, when patients or staff are already affected.

If patients deserve leading care, surely they also deserve leading environments.

HTM 03.01 is a detailed, authoritative document spanning more than 200 pages. It sets out expectations for ventilation in four broad categories of care:

• Surgical procedures.
• Medical care (wards).
• Mental health.
• Palliative care.

It also touches on diagnostic and support services.

Yet the weight of the document falls heavily on operating theatre design. This is its historic strength, evolving from DV4 in 1983 through to the latest 2021 edition. Theatres are highly controlled environments with dedicated plant, and as long as systems are maintained, most continue to function close to design intent.

Yet the balance is uneven. Mental health and palliative care, for example, receive only three lines each. No real design guidance is given. Ward areas are covered in less depth. In many diagnostic and support environments — places where patients and staff spend hours — guidance is minimal.

Ironically, estates professionals sometimes enjoy stronger statutory protection through local exhaust ventilation (LEV) regulations than vulnerable patients in cancer or psychiatric wards. Where LEV is governed by law, clinical ventilation guidance remains advisory.

The result is a patchwork. Some environments are 
well-protected, others not. Even where standards 
exist, they are enforced intermittently rather than continuously.

Ventilation is not just a clinical issue but a financial one. Operating theatres provide a clear example.

When a theatre’s ventilation fails, operations are cancelled. Staff time is lost. Patients wait longer. Trusts incur costs that are rarely budgeted for. Studies and estates reports often cite £20,000—£30,000 per day as the cost of a single theatre being out of action. That figure includes lost tariff income, wasted resource, and patient harm through delay. In large Trusts, failures can snowball into millions of pounds.

The economic case for monitoring is straightforward. The cost of installing closed-loop monitoring with redundancy is modest — often equivalent to a single day’s cancelled operating list. Running costs are negligible. Energy savings from trusted AHU setback or shutdown, once real-time monitoring is in place, can deliver up to 40 per cent reduction in annual ventilation energy spend.

In an NHS under constant financial strain, the argument writes itself. One day saved covers the investment. Every day after that is pure return.

From lag to lead: Practical solutions

Redundancy through air purification

It is entirely feasible to design low-cost redundancy into clinical ventilation systems. Supplementary air purification can remove particulates and volatile organic compounds, while fresh or conditioned air manages CO₂ dilution.

If the primary plant fails, a secondary system can activate automatically, keeping the environment safe. With an audit trail and continuous monitoring, estates teams can prove compliance and restore confidence. The shift from lag to lead transforms resilience.

Energy and Net Zero

HTM 03.01 already encourages AHU setback 
and shutdown strategies, but uptake is limited. Why? Because in an open-loop system, staff cannot be confident the environment remains safe during reduced operation.

With closed-loop monitoring, reassurance is built in. Staff see that air quality remains within safe limits. Estates can allow automatic secondary systems to respond if thresholds are breached. The result? Significant energy savings and reduced carbon footprint, aligning directly with NHS Net Zero commitments.

Patient safety: Surgical site infections

The evidence linking airborne contamination to surgical site infections is longstanding. Monitoring airborne particulates and microbes is the first step. Automating responses through supplementary filtration or directional airflow is the second. Together, these interventions reduce infection risk, shorten stays, and improve outcomes.

Staff wellbeing

During the COVID-19 pandemic, infection among healthcare staff was a major problem. In one clinical area we assessed, the airflow patterns caused contaminated air to be drawn across the nursing station — the very hub where staff congregated. PPE was in place, but PPE is the last line of defence and often fails in practice.

By installing supplementary purification, particulate levels dropped, and staff infection rates followed. Yet this was a reactive intervention — a lagging response. If monitoring had been in place, the issue could have been identified and mitigated proactively.

Case study: Lessons from the pandemic

Consider a real example from the pandemic. A department reported unusually high staff infections. Commissioning surveys confirmed that air change rates were technically within design requirements, yet the layout had evolved over decades. Supply air crossed the ceiling and was drawn directly towards the nursing station.

The result: concentrated exposure for staff. Retrospective action improved the situation, but dozens of staff had already fallen ill.

Had real-time monitoring been in place, early warning would have been possible. Estates teams could have acted before the infection curve rose. Supplementary engineering controls could have been triggered automatically.

This single example illustrates the cost of lag. Monitoring transforms response from retrospective to proactive, from lagging to leading.

Future design principles

Vector flows and low-level extract

Low-level extract behind patient beds, with supply air 
at the foot of the bed, ensures airflow crosses the 
patient and removes contaminants efficiently. This is particularly effective for heavier-than-air gases and airborne pathogens. Designers often prioritise ceiling supply for thermal reasons, but hybrid approaches are feasible: ceiling extract for temperature, low-level extract for safety.

Integration with BMS

Monitoring at extract points can feed into building management systems, providing estates professionals with a live view of ventilation performance. Beyond ventilation rates, approximate disease-risk indicators can be generated, empowering both staff and management with actionable insight.

Passive air cleaning as a safety net

If monitoring detects rising risk, supplementary air purification can activate automatically. The system shifts seamlessly from assumption to assurance.

Patient and staff confidence

Dashboards, displays, or even simple indicators can reassure staff and patients that their environment is safe. Just as heart rate monitors reassure clinicians, air quality monitors can reassure everyone who breathes the air.

Wider clinical environments

It is not just operating theatres that need attention. Wards, outpatient clinics, diagnostic areas, and mental health units all depend on safe air. Yet over 68% of clinical areas currently fall short of HTM 03.01 standards.

The backlog is growing, not shrinking. Maintenance and refurbishment cannot keep pace with demand. The result is a slow creep towards more environments with substandard ventilation.

Closed-loop monitoring does not solve every problem, but it makes deficiencies visible. Once measured, problems can be prioritised, mitigated, and addressed. Without measurement, issues remain hidden until harm occurs.

We began with a question: Do we lead, or do we lag? For too long, clinical environments have lagged. Failures are discovered only retrospectively, after patients or staff are harmed, after operations are cancelled, after costs are incurred.

It is time to lead. To operate closed-loop systems that measure, learn, and adapt in real time. To provide environments as safe and assured as the care delivered within them.

We only manage what we measure. The air we breathe is no exception. Without monitoring, invisible risks remain invisible. It is time to make the invisible visible — and in doing so, make British clinical environments the safest in the world.