Air hygiene in a pullet house: effects of air filtration on aerial pollutants measured in vivo and in vitro.

1. The natural history of air hygiene in a pullet house was assessed at three-weekly intervals using a combination of in vitro and in vivo assays. The performance of an internal air filter was also examined as an experimental technique for providing clean air. 2. Overall, air hygiene was poor by comparison with occupational standards for human health. The mass concentrations of respirable and inspirable dust were 1.4 and 11.3 mg/m3 compared to human exposure limits of 5 and 10 mg/m3 respectively. The concentration of ammonia was typically about 20 ppm. 3. The majority (greater than 99%) of airborne particles were non-viable. Commensal bacteria from the skin were the most numerous airborne bacteria. Scopulariopsis and Aspergillus spp. were the most prevalent fungi recovered from the air and bird's lungs respectively. The concentrations of airborne and lung fungi were positively correlated with ammonia concentrations. 4. The differences between in vivo and in vitro assays of airborne microorganisms suggest that an aerosol sampler should be devised which better mimics the physical and biochemical environment of the respiratory tract.