A method for determining correct performance of a sampling pipe in an aspirated particle and/or gas sampling system. The method includes causing a change in airflow n a sampling pipe of the aspirated particle and/or gas sampling system that induces a change in at least one airflow property within the sampling pipe, and detecting an effect of the change in said airflow property. Also disclosed is a method for determining correct performance of an aspirated particle gas sampling system. The method includes determining correct performance of a sampling pipe in the aspirated particle and/or gas sampling and determining correct performance of a detector in the aspirated particle and/or gas sampling system, wherein a test fluid is introduced to the aspirated particle and/or gas sampling system at or near the detector.