Predicting response times of fixed-temperature, rate-of-rise, and rate-compensated heat detectors by utilizing thermal response time index

A project was initiated to find a way of assigning thermal response time index (RTI) of heat detectors and to see if a detector response time could be estimated by utilizing the assigned RTI value. In phase 1 of the project, the concept was applied to fixed-temperature rating detectors and detector response times were successfully estimated. In the second part of the project, rate-of-rise detectors and rate-compensated detectors were investigated. Test data employing a plunge tunnel of varying air temperatures were used to extract RTI values of a rate-of-rise detector and rate-compensated detectors. In the final stage of the project, adequacy of estimating detector response times of rate-of-rise and rate-compensated detectors based on RTI values in conjunction with other threshold values for activation was assessed. Twenty-seven real-scale fire tests were conducted to see if the estimated response times match well with the measured detector response times. Test results showed that the detector response time estimation based on RTI values matched well with the measured ones. Having the ability of predicting detector response times in association of fire scenarios provides a great flexibility in deploying heat detectors in field operations. Detectors can be installed at performance-based spacing with respect to detector types and anticipated fire growth scenarios. Bench-scale tests to assign RTI values of detectors can replace the real-scale fire tests for the maximum spacing that are costly while less than reliable. Detector response sensitivity can be classified by the value of RTI and the maximum spacing of a detector can be assigned based on its RTI value.