Calibration and Field Testing of Passive Flame Height Sensors

Abstract

The concept of a passive flame height sensor involves thin strings permeated with fire retardant or solder which record heights of flame contact. Both types of sensors were calibrated during 12 experimental test fires with respect to flame heights measured on video tape. Three thresholds of fire damage to string-type sensors were identified: singeing of fine string fibers, complete blackening of the string, and thorough charring or consumption. These damage thresholds were found to exceed95%, 71% and48% of all flame heights measured from video tape, respectively. 18-gauge solder melted to a height exceeding 86% of measured flame heights. Field testing of 512 sensors during prescribed burning affirmed the potential practicality of this technique for estimating flame length.