EV components are exposed to a variety of influences during operation. And often they must also be protected against contamination and moisture. These tightness requirements are described, for example, in the definition of IP protection classes (IP = International Protection). IP protection class tests are type tests. In these tests, prototypes or samples are tested in the laboratory for resistance to the ingress of foreign bodies and moisture. The products are tested in strict accordance with the specifications of the desired IP protection class. The result is summarised in a test certificate, which strictly speaking only applies to the prototype or sample tested. To reduce the risk of delivering leaky products, these are tested during the manufacturing process as part of the quality control. The routine test is used to verify consistent product and manufacturing quality. When producing large quantities and especially in the automotive industry, it is common practice to test 100% of products for leak-tightness during production. The leak test integrated into the manufacturing process cannot be carried out under laboratory test conditions. Appropriate specifications (test pressure and leakage rate) must be defined here. The test parameters and test procedure are often defined in the specifications. However, this is not always the case, so parameters that are suitable and appropriate for the operating conditions of the product and its area of application must be defined. A close look at the loads occurring during operation of the product can be used to derive a suitable test pressure. And there are various approaches to determining a suitable leakage rate. An overview of industrial leak testing methods and important aspects of routine testing during production is provided. Practical approaches for determining test pressure and leak rate are presented.