Exposure to Hydrazine and its Control in Power Plants

Abstract

The use of hydrazine in power plants was surveyed with a postal inquiry to detect differences in exposure when alternative technical procedures were used in the handling of hydrazine. The exposure level of employees in eight plants was estimated based on the concentration of hydrazine in the air and the potential absorption through the skin. The questionnaire was sent to 288 power plants and 264 were returned, 100 of which used hydrazine. About 500 employees dosed and diluted strong (15% or 35%) hydrazine solution. The dosing was usually done with a pump or an ejector in bigger plants and with a measure in small plants. The airborne hydrazine concentrations in the rooms where hydrazine was handled were: < 0.01–0.06 ppm (mean < 0.02 ppm) for dosing with measure; < 0.01–0.37 ppm (mean 0.12 ppm) for dosing with pump; < 0.01–0.33 ppm (mean 0.09 ppm) for dosing with ejector, tank not closed; and < 0.01–0.04 ppm (mean 0.02 ppm) for dosing with ejector, tank closed and equipped with exhaust.

The time-weighted average (TWA) concentration of hydrazine in the air during the workday was estimated to be under 0.1 ppm. However, heavy exposure may occur if strong hydrazine is frequently splashed or spilled on the skin during handling. Because hydrazine is a suspected human carcinogen and sensitising agent, it is advisable to avoid even light exposure. Some methods to prevent dermal and inhalatory exposure are presented and discussed.