A new generator for producing propylene oxide vapor in inhalation toxicity studies

A vapor generator for propylene oxide which has a high vapor pressure (boiling point: 33.9 degrees C, vapor pressure: 442 mmHg at 20 degrees C) was developed. For inhalation toxicity studies, until now, there have been few generators capable of producing a low concentration of vapor from a liquid with high vapor pressure. In this study, the vapor was generated from the surface of a sintered sphere of glass beads filled with propylene oxide. The sphere was hung in a glass column which was installed in a Dewar vessel chilled with ice. The liquid of propylene oxide was automatically supplied from a reservoir to the sphere by capillary suction pressure caused by the evaporation of the liquid from the surface. The concentration of the generated vapor was able to be kept constant over a long period by using a carrier gas dried by a silica gel column, and could be regulated by the flow rate of carrier and dilution gas, and the sphere diameter. This generator is useful for the investigation of health effects of propylene oxide in inhalation toxicity studies.