1. Triethylene glycol in excess of saturation, introduced as a vapor into a cloud chamber in which a dynamic cloud of either meningopneumonitis virus or psittacosis virus was developed simultaneously with, or in most instances subsequently to, the glycol cloud, induced distinct reduction in concentration of air-home virus, as measured both by cloud sampling in capillary impingers and by exposure of mice to the cloud. The relative humidity in the chamber was held between 35 and about 60 per cent.
2. Reduction of virus concentration in samplers, in glycol runs as compared with controls, ranged from 0 to 93 per cent (average, 62 per cent).
3. Reduction of infective response in mice, based on counts of focal lesions on lung surfaces, ranged from 55 to 98 per cent (average 73 per cent).