AIR SAFETY
Lead or lag? Rethinking ventilation in the NHS
Hospitals across the NHS are rethinking ventilation as estates teams face growing challenges in ensuring safe air for patients and staff. Andrew Carnegie, Managing director at Air Sentry, says proactive monitoring and closed-loop systems are essential to transforming clinical environments from lagging to leading.
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: n Surgical procedures. n Medical care (wards). n Mental health. n Palliative care.
November 2025 Health Estate Journal 55
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
Air Sentry works with Torsa to integrate real-time environmental monitoring of a range of variables such as gases, noise, temperature and humidity, pressure.
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