<p>The aim of this bench study was to assess performance between currently available sidestream capnography sampling lines claiming compatibility with a Microstream™ enabled monitor system. A series of bench tests were performed on a selection of commercially available sampling lines (oral-nasal cannulas, PetCO₂ masks, and procedural bite blocks) to assess PetCO₂ accuracy, filter performance and mechanical durability. For each testing procedure, three separate sampling lines were assessed for five repetitions (n = 15 for each product). A 3D printed oral-nasal model connected to a lung simulator was set to two different breathing modes to simulate “normal” and “shallow” breathing. PetCO₂ accuracy measurements were completed at both breathing modes to simulate a variety of clinical scenarios, including oxygen delivery. Filter performance and mechanical durability were assessed for cannula sampling lines. When evaluating PetCO₂ accuracy across all sampling line types and breathing conditions, error estimates were lowest for matched-paired sampling lines, compared to cross-paired sampling lines. For oral-nasal cannulas, the matched-paired and three cross-paired performed within the system specification for “normal” breathing conditions. Split design oral-nasal cannulas consistently fell outside specifications under conditions of nasal obstruction. Five cross-paired filters clogged prior to expected threshold, with four demonstrating a clog capacity of less than half the expected value. Almost all sampling lines passed mechanical durability testing. Across all testing conditions, cross-paired sampling lines were observed to fall outside system specifications, suggesting that using sampling lines outside the Microstream™ family may disrupt accuracy of readings when using a Microstream™ enabled capnography monitor.</p>