Sterile swabs moistened with Whatman neutralizing solution(GE Healthcare, Little Chalfont, Buckinghamshire. UK) were used for Sampling 6 points during the morning shift, when the BLSA was operative: 2 points in the driver's cabin(the steering wheel and passenger's door handle) and 4 in the patient area(fixed oxygen delivery system flow meter, left handle of the stretcher, handle of the lateral access door, and cabin light switches).