Abstract: Hydrogen cyanide (HCN) is an important product released during cigarette combustion, which seriously endangers human health. However, traditional methods such as gas chromatography are difficult to achieve real-time measurements during the combustion process. In this work, the evolution of released HCN during cigarette combustion is researched by employing laser absorption spectroscopy (TDLAS) technique, where a distributed feedback laser with a central wavelength of 1.53 μm is selected as the light source. In the experimental system, a Herriott multi-path cell is used to increase the effective optical path of the laser, with 35 reflections and 17.5 m effective optical path, At the same time, the embedded system is used to collect and filter the absorption signal of the original demodulation, and finally the HCN concentration is calculated according to the measured spectral signal. In addition, wavelength modulation and demodulation spectroscopy are applied to improve the detection sensitivity and stability of the system. Calibration experiments show that the determination coefficient R2 of HCN is 0.9974 in the concentration range of 0.001%-0.01%. The system continuously monitors 0.002% standard HCN gas for 1000 s, and Allan variance analysis shows that the theoretical detection limit of the system reaches 22 × 10-9 within 55 s integration time, verifying the stability of the detection system. In order to study the evolution of HCN produced under different smoking conditions, experiments are conducted to simulate the release of HCN from cigarette combustion under different sampling flow rates from 100 ml/min to 400 ml/min and oxygen atmosphere of 17%, 22%, 30% and 40%. The results show that the HCN concentration released during cigarette combustion per unit time is positively correlated with sampling flow rate and oxygen concentration, while the total amount of HCN released during the entire combustion process is negatively correlated with oxygen concentration. This work provides a basis for further research on the generation mechanism of cigarettes are burned to produce HCN. and also provides an effective reference for the measurement of HCN and other trace gases in smoke in the near-infrared band.

Key words: hydrogen cyanide, laser absorption spectrum, cigarette burn, Allan variance