Should face-masks be worn by non-scrubbed operating room staff?

INTERVENTION: Operating theatres will be randomly assigned to be either MASK or NO‐MASK areas. Allocation of the theatres, according to the randomisation list, will occur immediately before the commencement of the operation list and will be concealed until then. All non‐scrubbed oroperating room staff will be asked to either wear or not wear masks during the operating list. The length of time spent in the theatre by any member of the non‐scrubbed team will vary according to their role in the team but may be between minutes to several hours. CONDITION: Surgical site infection PRIMARY OUTCOME: Surgical site infection: Any surgical site infection occuring before discharge or up to two weeks post discharge. SECONDARY OUTCOME: Compliance rate Cost INCLUSION CRITERIA: Non‐scrubbed operating room staff (including anaesthists).