A method for assessing a product, especially a smoking article or a filter element therefor, to determine product quality and/or product integrity, the method comprising the steps of: passing a gas sample through the product; directing the gas sample to a sensor assembly downstream of the product for detecting at least one flavour compound; and analysing the gas sample with the sensor assembly to detect the at least one flavour compound in the gas sample; characterised in that - holding the product or smoking article in a testing zone between a gas inlet and a gas outlet and generating a flow or stream of the gas sample through the testing zone from the gas inlet to the gas outlet, wherein the testing zone is located in a transport path which is provided to convey the product from a manufacturing equipment to a packaging equipment; and - the step of passing the gas sample through the product comprises streaming the gas sample through the product at a flow rate in the range of about 0.1 l/min to about 20 l/min, and wherein the sensor assembly comprises a plurality of sensors (S1, S2, S3) arranged in parallel, and wherein the step of directing the gas sample to the sensor assembly comprises switching a flow path of the gas flow from one sensor (S1, S2, S3) to another sensor (S1, S2, S3) after detecting the flavour compound in the gas sample. passing a gas sample through the product; directing the gas sample to a sensor assembly downstream of the product for detecting at least one flavour compound; and analysing the gas sample with the sensor assembly to detect the at least one flavour compound in the gas sample; characterised in that - holding the product or smoking article in a testing zone between a gas inlet and a gas outlet and generating a flow or stream of the gas sample through the testing zone from the gas inlet to the gas outlet, wherein the testing zone is located in a transport path which is provided to convey the product from a manufacturing equipment to a packaging equipment; and - the step of passing the gas sample through the product comprises streaming the gas sample through the product at a flow rate in the range of about 0.1 l/min to about 20 l/min, and wherein the sensor assembly comprises a plurality of sensors (S1, S2, S3) arranged in parallel, and wherein the step of directing the gas sample to the sensor assembly comprises switching a flow path of the gas flow from one sensor (S1, S2, S3) to another sensor (S1, S2, S3) after detecting the flavour compound in the gas sample. - holding the product or smoking article in a testing zone between a gas inlet and a gas outlet and generating a flow or stream of the gas sample through the testing zone from the gas inlet to the gas outlet, wherein the testing zone is located in a transport path which is provided to convey the product from a manufacturing equipment to a packaging equipment; and - the step of passing the gas sample through the product comprises streaming the gas sample through the product at a flow rate in the range of about 0.1 l/min to about 20 l/min, and wherein the sensor assembly comprises a plurality of sensors (S1, S2, S3) arranged in parallel, and wherein the step of directing the gas sample to the sensor assembly comprises switching a flow path of the gas flow from one sensor (S1, S2, S3) to another sensor (S1, S2, S3) after detecting the flavour compound in the gas sample.