Ethanol depletion dynamics in non-recirculating system breath alcohol simulators

Breath alcohol simulators are devices that use a heated ethanol/water solution to simulate human breath. Vapor created from heating the solution is commonly used to calibrate alcohol breath testing instruments. When the vapor of the same solution is repeatedly sampled, it causes the ethanol concentration to deplete at a currently unknown rate. The goal of this study was to quantify and better understand the ethanol depletion in non-recirculating system breath alcohol simulators. Simulators were filled with alcohol reference solutions, and air was pumped through the simulator and output to the analyzing instrument repeatedly until a change in concentration was observed, measured using infrared spectroscopy. Flow rates of 11, 16, and 21 L/min were tested to observe the impact of flow rate on depletion; concentrations ranging from 0.02 to 0.40 BrAC were tested to measure the impact of initial concentration on depletion. It was found that when observing different flow rates, the depletion of ethanol concentration was directly correlated to the total liters of air that passed through the system (r > -0.95). Altering initial concentrations showed that as the solution concentration increased, the rate of depletion of ethanol also increased. Our findings indicate that the total ethanol depletion in a non-recirculating system breath alcohol simulator can be described as a percentage of the original concentration being lost when a specific volume of air is passed through the system. We then calculated an equation that can predict ethanol concentration in the solution after repeated testing.