A photoacoustic (PA) leak detector on the base of a compact laser is proposed for the detection of hydrogen leaks from cooling systems of electric power generators. Leak detection is based on a trace gas marker registration, which is added to the gas carrier within the leakage area. Experimental results of impurity detection in weak gas leakage using a PA detector with a differential ring cavity flow type are sited. The threshold sensitivity of the detector is measured at . The effect of gas-flow rate through the detector is studied. The minimum reliably detectable flow is estimated to be , which exceeds the sensitivity of commercial helium and halogen leak detectors. Description and specifications of the developed model of a portable laser leak detector, designed in accordance with experimental results, are given.