This project will finalize the development of an advanced warning system for structural collapse for both new and existing buildings, particularly during structural fires. The project will utilize a non-contact ultrasonic sensor originally developed under NIST SBIR Topic 9.14 and extensively tested at Underwriters Laboratories (UL) under actual fire conditions through a follow-on DHS SBIR program. The ultrasonic sensor is capable of measuring changes in position, velocity, and acceleration from structural surfaces even in the presence of thick smoke, dust, or fog, which could render an optical or laser-based system unusable. Installation and alignment of the wireless sensor can be accomplished in a matter of seconds. The proposed system will integrate the ultrasonic sensor with conventional accelerometers to detect the vibrations and small changes in the position of a structure that are precursors of structural collapse. The collapse detection system will employ multiple sensors for distribution within and around the structure.