LAUSR

Abstract One of the most critical technical challenges in the field of fire safety is detecting the temperatures and concentrations of combustion gases mixed with smoke particles in fire environments. In this study, the absorption lines for the rotational transitions of carbon monoxide (CO) and nitric oxide (NO) were measured in the terahertz range 400–1000 GHz at room temperature and around 340 K. A signal-to-noise ratio of 140 for the absorbance of the J = 8–7 rotational transition for CO gas was achieved. This measurement approach allows simultaneous measurement of the temperature and concentration of each gas by reference to the Boltzmann plot of their absorbances. The temperatures obtained for both gases were consistent with those measured using a thermocouple within the respective 1-σ errors. Moreover, the concentrations derived by this approach agreed with the original gas concentrations within the respective 2-σ errors. Small temperature increases of ∼50 K from room temperature were identified. The accuracies of the derived temperatures and concentrations demonstrate the potential of terahertz spectroscopic sensing for diagnosing combustion gases in fire environments.