Helium leak testing is one of the oldest and most developed members of the family of trace-gas-based leak testing methods. Even though the title contains the word “helium,” this article is intended as an overview of trace gas methods in general.

From airbags to air-conditioning units and fuel rails, from anything implanted in the body to hermetically sealed enclosures for integrated circuits, there are some instances where the acceptable leak rate is so small as to be practically zero. Few air leak test methods, such as pressure decay, have the necessary detection range.