Air Volume vs. Air Quality: Does More Air Mean Better Protection?

Series Introduction
This article is part of a series that addresses common claims and misconceptions related to Temperature-controlled Airflow (TcAF) in operating room ventilation. Developed for technical consultants and architects working in hospital construction, this series compares TcAF with traditional Unidirectional Airflow (UDAF) systems using both scientific evidence and operational data. The goal is to provide a practical, technical foundation for informed design decisions in infection-sensitive environments.

Claim: “We know contamination levels are proportionate to the airflow. Since TcAF uses much less air, it cannot be effective.”

Reality: Airflow volume alone does not determine contamination control. Airflow design, distribution, and stability can be more critical than total air quantity.

Context and Analysis
In traditional design logic, higher airflow rates are often equated with cleaner air. This assumption has guided many OR ventilation implementations, which use high air change rates to achieve dilution or displacement of contaminants. However, cleanliness is not simply a function of volume, it is a matter of where and how air is delivered.

TcAF takes a targeted approach. The central surgical zone receives a higher effective air change rate due to a focused, gravity driven downflow, while the peripheral areas maintain a lower but still ultra-clean air exchange rate. This reduces unnecessary turbulence and energy use without compromising cleanliness.

Rather than dispersing contaminants, TcAF consistently pushes them downward and away from critical zones. Unlike UDAF, which introduce higher degree of lateral mixing at the edges due to velocity decay and turbulence, TcAF maintains a stable and predictable flow throughout the room.

Microbiological data from over 1,000 validation measurements confirm that TcAF achieves levels below 5 CFU/m³ in the entire OR and under 1 CFU/m³ in the wound area, despite using significantly less airflow than UDAF.

Conclusion
More air does not automatically mean cleaner conditions. TcAF demonstrates that effective airflow management, based on stability and targeted displacement, delivers superior contamination control with reduced airflow and lower energy demands.

This post is part of a continuing series addressing widespread claims about TcAF. In our next article, we examine the relevance of segregation testing when evaluating modern airflow systems.