A single feed system for maintaining different vapor concentrations in two inhalation chambers.

Two different concentrations of the same vapor can be maintained in adjacent dynamic inhalation chambers by using a single feed system which incorporates constant feed air flow rates and efferent tubes of unequal dimensions. For a given set of efferent tubes, the ratio of the air flow rates exiting the feed system and the resultant ratio of chamber concentrations vary as biexponential functions of the net negative pressure applied across the feed system. Depending on efferent tube dimensions and the negative pressure applied across the system, concentration ratios in the two chambers can be varied from 1:1 to 1:10. Three separate 30-day exposures were conducted using the system and observed mean daily vapor concentrations were within 3% of target concentrations.