Abstract: This article briefly describes the commonly used gas diffusion models and analyzes the engineering design standards and specifications of gas detectors. Using PHAST software, taking liquefied petroleum gas (LPG) and H2S as examples, the leakage diffusion is calculated, and the relationship between the concentration of combustible gases and toxic gases and time and space is obtained, determining the effective spatial area for setting fixed-point combustible gas detectors and fixed-point H2S detectors. Under the selected medium parameters, leakage scenarios, and meteorological conditions, the horizontal distance between the fixed-point combustible gas detector and the release source should not exceed 8.4m; the horizontal distance between the fixed-point H2S detector and the release source should not exceed 5.4m; if it is necessary to detect the first-level alarm value (volume fraction 0.005‰) within 4m from the H2S release source, then a fixed-point H2S detector should be set when the initial volume fraction of H2S in the leaked gas reaches 0.75‰ or above.

Key words: font-family:-apple-system, blinkmacsystemfont, ", font-size:14px, background-color:#FFFFFF, ">fixed, combustible gas, toxic gas, detector, leakage, diffusion

摘要： 简述了常用气体扩散模型，分析了气体检测器的工程设计标准、规格参数等。采用PHAST软件，以液化石油气（LPG）和H2S为例计算泄漏扩散，得到可燃气体和有毒气体浓度随时间、空间的变化关系，确定了固定点式可燃气体检测器和固定式H2S检测器设置的有效空间区域。在选取的介质参数、泄漏场景和气象条件下，固定点式可燃气体检测器距释放源的水平距离不应超过8.4m；固定式H2S检测器距释放源的水平距离不应超过5.4m；如果要在距H2S释放源4m范围内检测到一级报警值（体积分数0.005‰），则泄漏气体中H2S初始体积分数达到0.75‰以上时应设置固定式H2S检测器。

关键词: font-family:-apple-system, blinkmacsystemfont, ", font-size:14px, background-color:#FFFFFF, ">固定式, 可燃气体, 有毒气体, 检测器, 泄漏, 扩散