Hospital operating roans must meet one of the most complex sets of control requirements of any indoor environment if acceptable performance is to be achieved. The overall objective of this research project was to identify and demonstrate control strategies that could reduce energy requirements while riot producing deleterious effects on the environmental quality within the operating room.

The objective was achieved through an extensive literature search, through the development of mathematical and biophysical models, and through analysis of data obtained in two existing operating rooms (OR 1 and OR 5) with different system performance characteristics. OR 1 was designed in 1961 to supply 12 air changes per hour (ACH) of 100% outdoor air through high sidewall grilles and low sidewall return registers. OR 5 was designed in 1975 to supply 25 ACH, 20% of which was outdoor air, through ceiling diffusers and mid-height return registers on the wall . The ORs 1 and 5 actually delivered 12 ACH and 17 ACH, respectively, and OR 5 provided a minimum of 17% outdoor air.

No statistically significant differences in settling rates of total particulates in five size ranges were detected between the two operating rooms during occupied conditions that simulated surgery, but a trend toward less settling of viable particles was observed in the recirculated air systems. While the magnitude of the concentration and settling rates measured in operating rooms were less than those predicted in the mathematical model and measured in the biophysical model, the patterns were similar.

A control strategy was identified through mathematical and biophysical models that would result in less settling of the larger particles while reducing the total air exchange rate in the operating roans from 17 ACH to 12 ACH.

Units: SI