Abstract: A gas analyzer calibration apparatus. The apparatus operably connects between a monitored gaseous environment and a gas analyzer. The apparatus includes a vacuum pump for drawing test gases from the monitored environment through the apparatus and through the analyzer. A fluidic gate selectively allows or impedes the flow of test gases to the analyzer and provides calibration gases to the analyzer at the analyzer's demand rate, and may be heated to prevent the condensation of hot test gases flowing therethrough. The fluidic gate will pass both span calibration gases and zero calibration gases, as desired. A vacuum breaker provides atmospheric gases for use as a zero calibration gas.