As a security consultant, I have specified this system for both residential and commercial applications. I am an ASIS International Physical Security Professional (PSP) which is a tested qualification based on knowledge and understanding of security technologies. I also have 20+ years experience as a security design engineer in which I have studied, tested and evaluated technologies for function and limitations so that I can design solutions for my clients with best of breed solutions As a result, I have a thorough understanding of detection technologies. Also, I have a BS in Electrical Engineering, so I also have a technical background on the principles on how electrical devices function. It seems that the technician is describing a PIR (passive infrared) motion detector which detects heat energy changes. In order to defeat, the intruder would need to match the temperature of the overall environment. It would be highly unlikely that achieving the same temperature would be possible as the intruder would be sweating/raised adrenaline from the entry. It could be possible to “hide” IR energy within the space. So it could be possible that the sensor was not activated as the intruder was able to hide. I would then question the design and why (1) additional IR motion detectors were not installed to account for the technical limitations of IR detection and solid surfaces and (2) why a dual technology motion detector was not installed to account for interior obstructions. Dual technology motion detectors have both IR and microwave detection capabilities. The microwave detection can detect motion and not impacted by heat requirements.