Development Deregulating system for inhalation exposure to volatile organic chemicals (VOCs) for toxicity testing

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The workers using organic solvents are exposed mainly by inhalation. Therefore, experimental studies on the toxicity of organic solvents need to expose laboratory animals to accurate concentrations of them. We tried to make an automated solvent exposure system for small laboratory animals so that the ordered concentration could be obtained accurately and animals could be fed cleanly for a long-term experiment with a light labor. The exposure system mainly consists of four exposure chambers with feces wash out devices, four evaporators using commercial electric fuel injectors(EFIs), a vapor detector with automatic vapor sampling magnetic valves and a microcomputer with a recorder. The concentration in the chamber is continuously detected by the flame ionization detector (FID) and fed back to the microcomputer every 3 minutes. When the concentration deviate more than 5% from the ordered one, it is automatically adjusted. The time weighted average concentrations(TWAs) of n-hexane and toluene in one exposure were within 2% deviation from the ordered ones exceut 6% at 10 ppm n-hexane. The TWAs in long.term exposure of n-hexane and toluene fluctuated within 4% deviation from the ordered ones. Two kinds of organic solvents could be simultaneously exposed in the chamber. The exposure system was found enough accurate to generate solvent vapor and enough easy to feed laboratory small animals cleanly for a long-term experiment.