The aerodynamic characteristics of cat allergen.

To further characterize airborne cat allergen and a newly established cat challenge facility, airborne Fel d I levels and particle size distributions were studied in both the cat challenge room and home environments under different conditions of ventilation and physical activity. In the cat room, there has been a dramatic and continued rise in the concentration of airborne Fel d I since the room was established. No differences in total airborne Fel d I levels or particle size distribution were detected under widely differing rates of ventilation (40 air changes per hour vs 8 ac/hr vs < 1 ac/hr). Likewise, altering ventilation had little effect on the clearance of airborne antigen after disturbance. Significant increases in allergen levels were detected, however, after simply allowing the cats to leave their holding cage and move about the room. Fel d I levels in homes ranged from 2-468.5 ng/m3, similar to the levels seen in the cat room without disturbance. Fel d I particle size distribution was very consistent in both homes and the cat room with the majority of airborne Fel d I being detected on particles > 17 microm. Although very little allergen (< 15%) was detected on particles < 4 microm, this important fraction was present under all conditions. We conclude that airborne cat allergen resides primarily on relatively large particles, that a small but consistent fraction is found on very small particles, and that neither allergen levels or particles size distribution are significantly influenced by ventilation.