Abstract
After the ingenious studies of Blears and Leck, we have investigated the differential method of leak detection by using ionization gauges. We attempted a special probing technique and estimated the substitute sensitivity factor φ of ethylether, chloroform and aceton, at 5.4, 3.5, 3.5 respectively. And we also pointed out the complex phenomena in actual leak detection. With differential condensation and ionization gauges, the minimum detectable change in air was 1×10 -4μHg.
