A nude ionization gauge adjacent to the closed ion‐source chamber of a quadrupole mass spectrometer is a sensitive detector of the total amount of gas introduced for dynamic analysis. Linear relations between the amount of gas and the area of the ionization gauge pulse record were found for eight gases. For relatively unreactive gases, linearity extended to the smallest samples that could be detected, approximately 10−10atm cm3. Validity of the dynamic method of analysis was established by demonstrating that the same response was obtained for pulsed and for continuous sample introductions from calibrated leak sources of each of the eight gases.