Sartorius FLI SealTester performs seal testing of gas-flushed flexible food packaging. The first measuring belt applies a predefined pressure to the package and records the height of the package under pressure. The second measuring belt exerts a maximum possible pressure on the package without damaging it. If there is any leakage, the pressure applied will cause air or gas to escape. The third measuring belt repeats the process of the first measuring belt. If the package is gas-tight, the measured results of the first and third belts are identical. By contrast, if the two results differ, the package is leaky and automatically ejected.