A non-sterile plastic tube intended to conduct airflow pressure from a breathing mouthpiece to a parent device (e.g., spirometer) during pulmonary function testing (e.g., respiratory gas volume and flow). It is intended to function with a separate spirometry device and/or a pulmonary function analyser and is not intended to be integrated into a breathing circuit during respiration. A tube holder may be included as an accessory device. This is a reusable device intended to be cleaned/disinfected prior to use.