CONSTANT-VOLUME SAMPLING

An exhaust-emissions measuring technique in which the exhaust gases produced by a vehicle's engine are collected as it is driven through a test sequence of accelerations , decelerations , and cruise modes on a chassis dynamometer . A quantity of air is added to the exhaust gases until a specific volume (the same for all cars) is obtained. Concentrations of pollutants in the total sample are then analyzed for determination of their actual mass.