We report analyses by mass spectrometry of gases released from decrepitating fluid inclusions during progressive and controlled heating under vacuum. The results are presented graphically as gas abundance (AMU) relative to the temperature of decrepitation. Such data establish the composition of fluid inclusion assemblages with similar temperatures of decrepitation. A description of the technique, characteristics of the apparatus, analytical procedures, data treatment, and interpretation are presented. The advantages over the traditional gas analysis approaches by mass spectroscopy are also discussed.