Abstract: The application presented herein focuses on the gas flow control for the evaluation of lactose intolerance but is also consistent with flow control required in diverse applications such as, but not limited to: analysis of other disease states (either using chemical markers or using naturally occurring chemical composition analysis) from breath samples, analysis of chemical concentrations of contaminants in naturals gas production/delivery and in petrochemical processing, analysis of air samples for the detection of drugs and or explosives, detection of chemical composition for the optimization of growth of biological species and or compounds such as in fish farming and or phyto-plancton farming, and finally in the detection of release of carbon dioxide in the determination of an earthquake event.