Method for deciding on the timing of replacing a chemical filter, filter life detection sensor, chemical filter unit, and semiconductor manufacturing apparatus

摘要

A chemical filter unit 10 is made of a chemical filter 12 and a filter life detection sensor 1. The filter life detection sensor 1 is provided with an adsorption state detection sensor 3 and a reference sensor 4 to which a flow of air is blocked. The sensors 3 and 4 are made of the same filter material as the chemical filter 12 with a pair of electrodes sandwiching the filter material. An oscillation circuit, in which the sensors 3 and 4 constitute a part of the oscillating conditions, detects changes in impedance of the sensors 3 and 4 based on the changes in oscillation frequencies. A measurement of the adsorption state detection sensor 3 is corrected with a measurement of the reference sensor 4 in order to remove effects of temperature and humidity, obtain a measurement corresponding to the amount of adsorption of chemical substances, and decide on the timing of replacing the chemical filter based on the corrected measurement.