Improved methodology has been developed for generating controlled test atmospheres for inhalation toxicology studies. Vaporization of volatile liquids is accomplished in a 28 mm (outer diameter) glass J-tube in conjunction with a compressed air flameless heat torch, a pressure-sensitive switch and a positive displacement piston pump. The vaporization system has been very reliable with a variety of test materials in studies ranging from a few days to several months. The J-tube vaporization assembly minimizes the possibility of thermal decomposition of the test material and affords a better margin of safety when vaporizing potentially explosive materials.