For leak testing in accordance with DIN EN 1779 (1999) / EN 13185, helium 4.6 is used as a test gas. The test is able to detect minimal leakage rates and is considered the most sensitive test method for leak testing. In general, one should distinguish between an integral and local test method. In the integral test, leak rates (e.g. 1x10-7 mbar * l / s) can be determined, while the local testing enables the location of the leak to be determined using a spray probe. After passing a helium leak test, the thermowell or protection tube is labelled with a corresponding sticker.