Method for leak testing of a heat exchanger in a blood treatment device

A blood treatment device comprising:

• a fluid circuit and a heat exchanger, wherein the heat exchanger has two flow paths comprising a first flow path fluidically connected to a first section of the fluid circuit and a second flow path fluidically connected to a second section of the fluid circuit, and the fluid circuit is connected to an inlet and an outlet via the flow paths;
• a pressure sensor configured to detect a pressure in the first section of the fluid circuit of the blood treatment device;
• and
• a computing system adapted for monitoring a time curve of the pressure recorded by the pressure sensor in an evaluation period in which the blood treatment device has a test configuration, for checking whether the time curve of the pressure in the evaluation period satisfies one or more predetermined criteria, and for determining a leak of the heat exchanger when the time curve satisfies the one or more predetermined criteria,
• the first section of the fluid circuit in the test configuration being fluidically separated from the second section of the fluid circuit and/or the inlet and/or the outlet using one or more switching elements, and
• monitoring the time curve in the evaluation period comprises monitoring the time curve in a first evaluation period during a conveyor operation for pressure build-up/negative pressure build-up in the first section and/or the second section of the fluid circuit and/or monitoring the time curve in a second evaluation period after a pressure build-up/negative pressure build-up in the first section of the fluid circuit.