The major parameters affecting temperature inside inhalation chambers

Variations in inhalation chamber temperature can produce alterations in animal physiology, metabolism of foreign compounds as well as the chemical interaction of pollutant aerosols. This report presents the results of an investigation of the different mechanisms of heat transfer in a 380 L inhalation chamber and discusses the relative effectiveness of various methods that may be used to maintain a uniform chamber temperature during animal exposures. The thermal characteristics of the inhalation chamber were studied using an array of 40 thermocouples, with and without rats in the chamber and with and without 5 cm fiber glass insulation surrounding the chamber. Temperature profiles were measured with different animal loadings and intake air temperatures. An effective heat transfer coefficient of 6.6 +/- 1.8 W/m2 degrees C was determined for the stainless steel walls of the chamber. Heat balance studies with rats in this chamber have shown that with room air intake at a flow rate of 100 L/min, the stainless steel chamber walls were effective at removing approximately ninety percent of the animal heat as compared to the airstream.