Comparison of three ventilating systems in an operating room

Observations on the bacteriological contamination of the air have been made in an operating room fitted with three alternative systems of ventilation. These were; A, downward displacement ‘piston’; B, moderate velocity turbulent; C, low velocity turbulent. The volume of the ventilating air supplied was the only characteristic of the ventilation which affected the contamination levels reached during operations. No significant differences could be detected between the three ventilating systems in this respect. Unavoidable temperature differences in the operating room render it generally impossible to produce effective downward displacement air movement with ventilating air supplies which do not exceed 1500 ft. 3 per minute over a ceiling area of 300 ft. 2 . Great differences were observed between the several carriers of Staphylococcus aureus in the extent to which they dispersed this organism into the air when working in the operating room.