Filter system with a secondary filter element and a primary filter element, and use of a secondary filter element in a filter system

A filter system comprising:

• a housing comprising a fluid inlet and a fluid outlet;
• a primary filter element and a secondary filter element arranged in the housing between the fluid inlet and the fluid outlet, wherein the secondary filter element is arranged in a hollow interior of the primary filter element and wherein the secondary filter element comprises a coupling device;
• wherein the primary filter element and the secondary filter element are configured to be flowed through sequentially by a fluid to be filtered;
• wherein the housing comprises at least one coupling element disposed at the fluid outlet and configured to couple to the coupling device of the secondary filter element;
• wherein the secondary filter element comprises a filter medium body permeable for the fluid to be filtered, wherein the filter medium body of the secondary filter element extends along a longitudinal axis and surrounds a hollow interior of the secondary filter element, wherein the filter medium body of the secondary filter element comprises an open end and a closed end positioned oppositely to the open end along the longitudinal axis;
• wherein the filter medium body of the secondary filter element comprises an adsorption agent;
• wherein the coupling device of the secondary filter element is arranged at the open end of the filter medium body of the secondary filter element;
• wherein the coupling device of the secondary filter element is configured to be coupled rotationally fixed to the primary filter element;
• wherein the coupling device of the secondary filter element comprises a thread and wherein the at least one coupling element of the housing comprises a thread complementary to the thread of the coupling device of the secondary filter element;
• and
• wherein the thread of the coupling device of the secondary filter element is configured to engage the thread of the at least one coupling element of the housing.