Risk probability evaluation for the effect of obstacle on CO₂ leakage and dispersion indoors based on uncertainty theory

Carbon dioxide is a common gas in the chemical industry, and it is asphyxiating. A test system was established to determine the characteristics of indoor gas diffusion. The system comprised an enclosed space, gas discharge system, data acquisition system, and obstacle. CO₂ gas concentration due to an indoor leak was measured, and characteristics of CO₂ diffusion indoors in the presence of an obstacle were elucidated. The effects of obstacle height, obstacle width, and obstacle–leakage distance on gas diffusion were determined. An obstacle was discovered to hinder CO₂ diffusion in the enclosed space. With increasing obstacle height, the gas was more likely to accumulate in front of the obstacle before spreading on the ground around the side of the obstacle. CO₂ accumulation behind the obstacle was mainly due to ground accumulation rather than direct accumulation from the leakage source. However, the difference in CO₂ concentration in the interior space was negligible for different obstacle heights. Obstacle width only weakly affected the concentration of CO₂. Obstruction reduces the volume of space available to a gas. To minimize misjudgment, risk probability evaluation of the dense-gas leakage was proposed based on uncertainty theory. The combined standard uncertainty was calculated in specific cases, and the probability of misjudgment in risk evaluation was determined. The results provided scientific basis for early detection and rescue strategies during indoor CO₂ leaks in the presence of an obstacle.