The German GS mark is a voluntary safety mark. It is not a universal quality seal, but is meant to ensure that the technical requirements for the safety of a product are met and will be monitored by an independent testing company such as TÜV Rheinland. All effects of the product on health and safety of humans are covered by the tests. Very different tests may be necessary, depending on the product.
The manufacturer must arrange for the product to receive a so-called "type test" by an evaluation body such as TÜV Rheinland. TÜV Rheinland carries out the required tests in recognised laboratories worldwide.
TÜV Rheinland performs checks to maintain the certification. Tests are carried out to ascertain whether the manufactured product still conforms to the tested type or whether changes have been made. Such inspections, which usually take place on an annual basis, also include a control of the quality system as well as the final examination. The aim is to determine whether mass production can ensure the safety requirements for the product.
The award of the GS mark is governed by the Product Safety Act and limited to a maximum of five years. It expires automatically if there is any change to the tested product.
Certified products may be labelled with the GS mark.
More information can be found here.