For each exposure,six ChR-CD male rats, weighing 240 to 257 grams, were exposed to the test material in a 16-liter bell jar for four hours unless all died sooner. The test material was metered at a uniform rate into a heated (100C) stainless steel T-tube by a syringe drive. Houseline air was used as a diluent to give the desired atmospheric concentration. The nominal concentration was calculated on the basis of air flow and weight of material used. For analysis of H-6396, gas samples were taken periodically from the chamber exit and analyzed by a gas chromatographic method. Survivors were sacrificed 14 days later. No histopathologic studies were made.