A respiratory gas monitor testing system having a respiratory gas monitor coupled to a system for detecting a leak, wherein the system for detecting a leak has a flowmeter in fluid communication with both an inlet and an outlet of the respiratory gas monitor, with the exhaust of the flowmeter venting to atmosphere a restriction valve, a sample pressure sensor, a flowmeter valve configured to allow the flowmeter to either measure sample flow rate or leak rate, a flow-smoothing buffer configured to improve flow measurement accuracy, and a system for simulating human breath wherein the system for human breath at elevated airway pressure has an air source, a calibration gas source, a breath simulation valve, a calibration gas valve, a sample pressure sensor, an air reservoir, a pressurized bottle with a pressure regulator and an orifice, and an air pump.
