During the operation of a Tissue-Tek III? Vacuum Infiltration Processor in a small unventilated room, the concentration of three reagent vapors—formalin, xylenes and isopropyl alcohol—was measured by continuous air sampling. The experimental data indicate that an employee's exposure to these vapors while operating this particular tissueprocessing unit during an eight-hour shift would be less than OSHA's eighthour time-weighted average (TWA) limits by one to two orders of magnitude. Furthermore, calculations reveal that these OSHA limits would not be exceeded even if the employee were positioned directly in front of the tissueprocessing unit during its entire 13-hour cycle. Even when the activated-carbon filter was removed from the air venting system, the vapor levels remained below OSHA limits. This study indicates that a substantial margin of safety regarding inhalation exposure to these toxic substances has been engineered into the unit's design, which incorporates a closed retort and controlled air system.
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