Development of a new respirator for organic vapors with a breakthrough detector using a semiconductor gas sensor

A method for determining breakthrough of organic vapors in a respirator cartridge was developed. A thick film semiconductor gas sensor was used as a breakthrough detector. Air containing organic vapor was introduced into the cartridge, and an output signal from the sensor inserted in the downstream flow of the cartridge was recorded on an IC card. Simultaneously, the breakthrough curve was obtained by measuring the vapor concentration at downstream from the respirator cartridge with a gas chromatograph (GC) equipped with a flame ionization detector. When the breakthrough was almost completed, the data recorded in the card were transferred to a personal computer and the change in the output signal from the sensor was compared with the breakthrough curve obtained by the GC. Twelve organic solvents including aromatic hydrocarbons, chlorinated hydrocarbons, acetates, alcohols, ketones, and aliphatic hydrocarbons were tested under low (20%-25%) and high (70%-80%) relative humidity ranges. The sensitivity of the sensor for chlorinated hydrocarbons such as 1,1,1-trichloroethane was relatively low, especially when the relative humidity was high, but the rise time of the sensor output signal was almost the same as or earlier than the breakthrough time by the GC. Based on the experimental results, a new respirator for organic vapors that can detect the end of service life was developed.