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Evaluation of a recently designed multi-tiered exposure chamber

We have evaluated a newly designed multi-tiered chamber intended for inhalation studies. Our particular concerns were the aerosol concentration distribution within the chamber and the resultant lung deposition in exposed animals. Our findings may be summarized as follows: aerosol concentrations were found to vary only 5-9% for different locations within the chamber for a variety of conditions tested; aerosol size distributions were constant throughout the chamber; lung deposition in rats was also found to be quite uniform for rats at different locations throughout the chamber; light levels and ammonia levels were acceptable; and animal handling characteristics were excellent. We have found this to be an excellent chamber which combines the economic advantages of reduced animal care and floor space requirements with good aerosol distribution characteristics. Because of the slight side-to-side variation in concentration it would be advisable, as a precaution, to rotate animals from tier to tier throughout a chronic exposure so that animals spend equal times on each tier.