What is leak testing by gas sniffing method?
The gas sniffing leak testing method (“sniffer”) involves applying gas other than air to the tested element at a certain pressure and detecting the presence of that gas in the surrounding environment by using a test probe with a sensor appropriate for the particular type of gas. The probe with a gas sensor is slowly moved along the tested product, “sniffing” the joints, seals, seams, welds and other elements where a leak may occur.
Various gases or gas mixtures are used for gas leak testing, e.g. helium, hydrogen, carbon dioxide, sulfur hexafluoride (SF6), propane, butane, and others. Since many gases may pose a threat to the operator (e.g. flammable, explosive gases) or the environment (refrigerants, freon), technical gases are most often used, which are safe and cheap, like 5% hydrogen solution in nitrogen (5% H2 / 95% N2).
Gas methods are usually used for very demanding tests that cannot be solved by simpler and cheaper air methods (very small leaks, very large volumes, high temperature of the tested item, localization of the leak). For the most restrictive requirements, helium leak detectors are used, equipped with a mass spectrometer.