[Experimental studies of long-term aerosol inhalation. Inhalation chambers and their operation characteristics...

In an attempt to develop the technique for long-term inhalation studies, a "multipurpose" inhalation system was devised. Using this system, an experimental model of the human polluted lung was successfully produced in rats after long lasting inhalation of heavy oil combustion products as a model aerosol. Facilities for concentration regulation of the particulated matter and the actual concentrations obtained throughout this experiment were described in the previous first report. In this second report, newly devised two types of inhalation chambers are described. One is a typical pyramidal type chamber of about 1 m3 with a newly devised exhaust orifice and another is an economical plane cubic type chamber of about 200l. Their operation characteristics, i.e., distribution of the particulated materials and maintenance of biological environment in the chamber were determined on a series of preliminary experiments under various air exchange rates. From the results routine performance discipline has been established. Data in the biological environment obtained from continuous operations of this inhalation system for over three years are also described. Occurrence of unfavorable respiratory infection was successfully avoided throughout those life long experiments, making the average life span and the main cause of the death of the animals satisfactorily acceptable.