RESUMO
The present study concerns the air quality and microbiological contamination in two newly built operating theatres; one with laminar air flow (LAF) equipment for cardio-thoracic operations, and one with conventional ventilation for urological operations. Both theatres had an identical number of air exchanges (17/h), identical microclimatic conditions and they employed the same cleaning procedures. In the LAF-ventilated operating theatre bacterial contamination of the air was effectively reduced to less than 10 colony-forming units (CFU)/m3 in all 125 samples (1 m3 per sample) tested. In most samples, 118/125, the bacterial count was less than 5 CFU/m3, despite the presence of ten persons. The conventionally ventilated theatre reached values up to 120 CFU/m3 during the most active period of the day when approximately seven persons were present. The LAF ventilation reduced both the content of particles in the air and contamination by bacteria on the floor. In both theatres cleaning procedures had only a low impact on CFU in the air and on the floor. The use of diathermia markedly increased the level of small particles in the air, and this may influence the air quality in the operating theatres.