This study investigates the performance of the mobile Cortex Metamax 3B (MM3B) automated gas meter in simulated and actual workouts involving teenagers. Is the MM3B trustworthy enough to measure expired ventilation (VE), consumption (VO2), and carbon dioxide generation after several measurements using the Tester (both percentage error and percentage technical error of 2% measurement)? on a range of simulated metabolic rates using the Gas Exchange System Validator (GESV) (VCO2). Research has shown that MM3B is stable at the permitted range during 3 hours while monitoring the gas fractions, as well as the VE, VO2, and VCO2 created by GESV, especially at moderate and high metabolic rates (2% deviation and modest physiological significance). MM3B rated both VO2 and VCO2 significantly higher by about 10-17% at moderate and strenuous activity than DBM and at all exercise levels than Oxycon Pro, although without a significant margin of error. in VE. Between the two criteria systems, none of the metabolic variables showed any discernible change. (DBM and Oxycon Pro). The MM3B provided acceptable data on stability and reliability, but it was decided that without further adjustment for VO2 and VCO2, the data were not valid during moderate and strenuous activity