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In this study, we investigated the time course effect of sensory eye irritation in 16 subjects exposed (i.e., eye only) to n-butanol and 1-octene. Half the subjects were exposed to n-butanol, and the remaining subjects were exposed to 1-octene. Each subject was studied on 5 different days; during each day each subject was exposed in three runs (i.e., run 1, run 2, and run 3) to a constant concentration of either n-butanol or 1-octene. We performed run 1 and run 3, both of which lasted 15 min each, to evaluate persistence in "sensitization." We performed run 2, which lasted 60 min, to study the time course of sensory irritation. Ratings of ocular irritation intensity were obtained continuously during all three runs. The exposure concentrations for n-butanol were 0 mg/m3, 300 mg/m3, 900 mg/m3, and 3 000 mg/m3, and the exposure concentrations for 1-octene were 0 mg/m3, 6 000 mg/m3, 10 400 mg/m3, and 18 000 mg/m3. During run 2, we observed a slight increase in perceived eye irritation intensity for the lower concentrations of 1-octene and for all exposure concentrations of n-butanol. However, the threshold for irritation was clearly exceeded for only the 1-octene 10 400-mg/m3 and 18 000-mg/m3 exposures. During these two exposures, the response increased 10-fold following 20-40 min of exposure during run 2, after which the response remained constant. We investigated the existence of persistence in "sensitization" by comparing intensity of responses between run 1 and run 3. Persistence in "sensitization" was apparent for only the 1-octene exposure.