Airborne infection in a fully air-conditioned hospital. II. Transfer of airborne particles between rooms resulting from the movement of air from one room to another.

Experiments were conducted simultaneously with gas and particle tracers to determine the relative loss of particles between source and recipient sites in the hospital ward units. The magnitude of this loss could be accounted for by the assumption of sedimentation from well-mixed air masses during the time required for movement between source and recipients sites. As a consequence of this loss the degree of isolation between patient rooms for airborne particles was between 4 and 25 times greater than that for gaseous contamination, which reflects the actual transport of air between the rooms. The design and construction of portable spinning-disk particle generators suitable for field studies is discussed.