Sufficient quantities of quality air and controlled, unidirectional flow are important elements in providing a safe building environment for operating rooms.

To make dynamic assessments of an operating room environment, a validated method of testing the multiple factors influencing the air quality in health care settings needed to be constructed. These include the following: temperature, humidity, particle load, number of microbial contaminants, pressurization, air velocity, and air distribution. The team developed the name environmental quality indicators (EQIs) to describe the overall air quality based on the actual measurements of these properties taken during the mock surgical procedures. These indicators were measured at 3 different hospitals during mock surgical procedures to simulate actual operating room conditions. EQIs included microbial assessments at the operating table and the back instrument table and real-time analysis of particle counts at 9 different defined locations in the operating suites. Air velocities were measured at the face of the supply diffusers, at the sterile field, at the back table, and at a return grille.

The testing protocol provided consistent and comparable measurements of air quality indicators between institutions. At 20 air changes per hour (ACH), and an average temperature of 66.3°F, the median of the microbial contaminants for the 3 operating room sites ranged from 3-22 colony forming units (CFU)/m³ at the sterile field and 5-27 CFU/m³ at the back table. At 20 ACH, the median levels of the 0.5-µm particles at the 3 sites were 85,079, 85,325, and 912,232 in particles per cubic meter, with a predictable increase in particle load in the non–high-efficiency particulate air-filtered operating room site. Using a comparison with cleanroom standards, the microbial and particle counts in all 3 operating rooms were equivalent to International Organization for Standardization classifications 7 and 8 during the mock surgical procedures.

The EQI protocol was measurable and repeatable and therefore can be safely used to evaluate air quality within the health care environment to provide guidance for operational practices and regulatory requirements.