Gas leak detection is the elementary testing of gas pipe parts for existing leaks. A gas pipe is considered leak-proof when there are no gas leaks from the exposed parts. This means that exposed gas pipes in particular are checked for external leak tightness. Leaks are detected by testing a connection point; e.g. at fittings, flanges, screw fittings and gas control valves. It is also important to check ducts entering buildings and gas pipes concealed in cavities at the air outlets. The most up-to-date way to detect gas leaks is to use an electronic gas detector (“sniffer”).