We present a case in which the Dräger Primus (Dräger Medical AG&Co KG, Lüberck, Germany) anesthesia monitor displayed false readings of low end-tidal carbon dioxide (Etco2) immediately after intubation. The patient’s physical examination, vital signs, and arterial blood gases were normal. The ventilator, circuit, gas sample line, and water trap appeared intact and functional. A second gas analyzer revealed normal Etco2 readings, correlating with blood gas values. The defective monitor gas flow rates and gas calibration values were inappropriately low. Partial opening of the solenoid zero valve allowed entrainment of room air, which caused artifactual dilution of the gas sample.