Diode Laser Measurements of HF Concentrations From Heptane/Air Pan Fires Extinguished by FE-36 and FE-36 Plus APP

Abstract

Tunable diode laser absorption spectroscopy (TDLAS) is used to measure the time evolution of hydrogen fluoride (HF) concentrations produced from a series of enclosed heptane/air pan fires extinguished by FE-36 or FE-36 plus ammonium polyphosphate (APP). Recent advances in room-temperature fiber-coupled near-infrared (NIR) diode lasers provide isolation of the laser and signal-processing electronics from the hostile sampling site. For the fires studied, the change in HF gas concentration with time is dependent upon the fire-fighting chemical used to extinguish the fire. The presence of APP is observed to accelerate the dissipation of HF from the fire enclosure. Visible attenuation spectroscopy is also used to measure the amount of light attenuation (obscuration) that occurs as a hand-held fire extinguisher containing powder fire-fighting agent is released in the crew space of a Ml-Abrams land combat vehicle. Obscuration tests demonstrate that release of APP from extinguishers in an occupied space does not present a visibility challenge to the vehicle personnel.