Formation and detection of hydrogen fluoride gas during fire fighting scenarios

Hydrofluorocarbon-based (HFC) fire extinguishing agents generate hydrogen fluoride (HF) gas [HF(g)] during thermal decomposition. Potential HF(g) exposure represents a health risk to any personnel not wearing proper Personal Protective Equipment (PPE) during scenarios where HFC extinguishers are deployed. HF(g) is harmful to humans at vapor concentrations greater than 3 parts per million (ppm), with an Immediately Dangerous to Life and Health (IDLH) level of 30 ppm. Controlled live-fire tests with HFC fire suppression confirm that HF(g) is produced at concentrations that greatly exceed IDLH levels within seconds and demonstrate the need for real-time detection of HF at high concentrations and within very short time frames. Current commercial sensors are limited in capability for measuring high concentrations of HF in the vapor phase, and within the time frame required to prevent exposure to dangerous levels of this toxic gas. This review provides a comprehensive overview of HF detection methods, including colorimetric, electrochemical, mechanical, and optical sensors. The applicability of sensor types to HF detection within the complex environment of a fire event is evaluated regarding response time, selectivity, and sensor saturation.