Tracer gas detection
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 SF6 and other electron capturing compounds and can detect leak rates as low as 1x10-7 ml/sec SF6.
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 a high oxygen content has been determined.
The technique is similar to helium leak detection which uses a mass spectrometer detector. One advantage of sulphur hexafluoride as a test gas is that it has a higher molecular weight that helium and less likely to give a false "leak" result from gas permeation through the packaging material.