Gas leak detection systems are used to "sniff" for a test gas which has been earlier introduced into the package.
Smithers Pira uses a Qualitek leakmeter 120 electron capture detector. The leakmeter 120 responds to sulphur hexafluoride (SF6) and other electron capturing compounds and can detect leak rates as low as 1x10-7 ml/sec.
The gas is injected into the test package and the injection point sealed with tape. The leakmeter fitted with a miniature "sniffer" probe is used to locate any leakage routes.
The technique is easily capable of detecting microleaks in non-porous medical device packaging and modified atmosphere (MAP) food packaging. In the latter application it is often used to identify leakage routes after high oxygen content has been determined.
The technique is similar to helium leak detection which uses a mass spectrometer detector. One advantage of SF6 as a test gas is that it has a higher molecular weight than helium and therefore less likely to give a false "leak" result from gas permeation through the packaging material.