For highest sensitivity and greatest accuracy.
The heart of the most sensitive and accurate instrument for detecting extremely small leaks is the mass spectrometer, which is used to measure the rate of flow of a tracer gas through leaks using vacuum, pressure or vacuum-pressure techniques. The mass spectrometer detects the tracer gas and converts it to an electrical signal proportional to the size of the leak. Helium is usually used as a tracer gas because of its unique combination of properties:
- Helium is extremely rare in the atmosphere, so there is little ambient “noise” to interfere with leak measurement
- Non-explosive, non-toxic, completely inert (no contamination of the tested product)
- Will not contaminate and desensitize its own detector as is common with detectors using other tracers
- Helium is a small, light molecule (mass 4) and will flow readily through extremely small leaks