Technical cleanliness is at the centre of attention in more and more sectors of the automotive industry. Its importance primarily lies in the need to ensure the correct function of components and it is necessary to take into account that impurities can affect the assembly and proper functioning of other components if they are connected together in the working circuit. Requirements for technical cleanliness vary according to the type and function of components and can be divided into two basic areas - chemical cleanliness (for example, lubricant contamination) and particulate cleanliness (particles and fibres). So-called clean production must include all areas up until final assembly - production, assembly, storage, transport and the packaging itself. In process chains, measures are taken to minimise contamination or particle generation to achieve a continuous and controllable standard of cleanliness. A special section is the cleanliness of the cable connectors, which is dealt with in this article. The introduction describes the current state of science and research in this field and then summarises the standard requirements in the automotive environment and the basic possible consequences of connector contamination. This is followed by a case study showing the possibilities of preventing contamination by particles and fibres, including a discussion of the effectiveness of these measures.