At 6:35 a.m. on Monday, November 9, 2009 the Toxic Gas Monitoring system broadcast a building evacuation message, and the building was evacuated. The BNC staff responded immediately, as did the Purdue Fire department. Normal evacuation procedures were followed, and the building was secured by BNC's Emergency Response Team and the Purdue Fire department. The cause of the alarm from the TGM was first thought to be a software error in the monitoring system but the staff subsequently traced the issue to a bad NH3 pressure transducer measuring the interstitial pressure on the double-walled ammonia line at a Valve Manifold Box in the subfab. The pressure signal dropped momentarily to zero and then returned to normal levels. The intermittent drop-out was just long enough to trigger an alarm. The defective sensor has been replaced and will be sent to the manufacturer for analysis. All gasses are back on and the building has returned to full operation. Thank you for your patience with this momentary disruption of process services. Ron