A Metabolic Cart measures: Pulmonary Ventilation of every breath, Oxygen concentration – both inspiratory and expiratory, Carbon Dioxide concentration – again both inspiratory and expiratory, Also ambient Temperature, Pressure, & Humidity. Temperature, Pressure, & Humidity are used to convert the metabolic data from Atmospheric conditions to Standard Temperature, Pressure and Dry conditions, or STPD. Finally, this measurement data is used to calculate O2 Consumption and CO2 Production and other Metabolic Data.