Airborne and Surface Bacteria in ORs: Integration of ASHRAE-Compliant Ventilation and Active UV-C Air Treatment

Bacteria in ORs increase surgical site infection risk. The American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 170 defines OR ventilation standards, but the added benefit of in-room supplemental ultraviolet C air treatment remains uncertain. We compared bacterial counts before and after installing active ultraviolet C air treatment in an OR with Standard 170-compliant ventilation, using a similar OR as a control with Standard 170-compliant ventilation alone. After installation, the intervention OR showed 80% fewer airborne bacteria and 61% fewer settled surface bacteria. The control OR showed a 219% increase in airborne colony-forming units per cubic meter and a 24% increase in settled surface bacteria over the same period, reflecting potential confounders. Although the intervention was associated with lower bacterial levels in two assays, more evidence is needed given the limited number of ORs tested and the variation in the control OR.