Test chamber and method

A method for conditioning air in a temperature-insulated test space of a test chamber, the test space being closable to an environment and serving for receiving test material, a temperature ranging from −40° C. to +180° C. being generated within the test space by a temperature control device of the test chamber, a temperature ranging from −50° C. to +180° C. being generated within the test space by the temperature control device, the temperature control device having a heating apparatus and the cooling cycle having a refrigerant, a heat exchanger disposed in the test space, a compressor, a condenser and an expansion element, the refrigerant being a hydrocarbon or a refrigerant mixture made of hydrocarbons, wherein the cooling cycle has a pressure compensation pipe, which extends between a high-pressure side positioned downstream of the compressor and a low-pressure side positioned upstream of the compressor of the cooling cycle, and the pressure compensation pipe is connected between the stop element and the compressor, the method comprising preventing a reflux of refrigerant in the heat exchanger in the opposite direction of flow by the stop element that is disposed in the cooling cycle directly downstream of the heat exchanger with no other pipes or valves being connected in the section of the cooling circuit between the heat exchanger and the stop element and upstream of the compressor.