Influence of wearing masks on the density of airborne bacteria in the vicinity of the surgical wound.

To find out if the wearing of masks influenced the number of colony forming units (CFU) of bacteria in the vicinity of the wound, 14 operations on the thyroid gland were divided in 30 min periods during which personnel were randomly allocated to wear or not to wear masks. There was at least one period with, and one without masks during each operation. Air was sampled 20 cm from the wound using a Sartorius membrane filter sampler. There were no significant differences between the groups in either numbers of CFU or species of pathogenic bacteria found.