Background: A locally installed air purifier unit (Novaerus Protect 800) has been shown to reduce the air bioburden in an intensive care unit and the incidence of healthcare -associated infections. Aim: To explore whether this type of air purifying unit could reduce bacterial concen-trations in the air of an operating room (OR) during orthopaedic surgery, thereby reducing the risk of surgical site infections. Methods: In this prospective experimental study, undertaken in 2018, three air purifying units were installed in an OR in a Swedish hospital in 2018. The air was actively sampled during 11 operations by a slit-to-slit agar impactor with the air purifying units either switched on or switched off. Air movements were visualized with the aid of smoke in mock-up studies. Findings: No significant difference in bacterial concentrations in air was found between the two conditions (air purifying units switched off or on) (P1/40.54). Air movements around and above the surgical wound were disordered and resembled those of dilution mixing air. Conclusion: The three air purifying units installed in the OR did not reduce the airborne bacterial levels in the critical zone during orthopaedic surgery.
