Gases, vapors, liquid sprays, aerosols and other forms of ignitable fluids dispersed into the atmosphere, under certain circumstances, may encounter a hot surface. When investigating a fire, it may be necessary to determine in such cases if the hot surface was a competent ignition source. The paper reviews the available experimental data and findings on this topic and gives appropriate advice. It is shown that, unlike the autoignition temperature (AIT), which is only slightly dependent on test conditions, the hot-surface ignition temperature (HSIT) is highly dependent on the test environment conditions. The primary variable affecting the outcome is the degree of ‘enclosedness.’ If the degree of enclosedness is not extreme, a standard recommendation is that the hot-surface ignition temperature might be assumed to be 200°C higher than the AIT. But for conditions of significant enclosedness, the actual ignition temperature is more influenced by the fuel’s volatility (which is related to its flash point) than its AIT value. Higher volatility fuels are harder, not easier, to ignite from a hot surface. Since gasoline is the most volatile of the common automotive-use ignitable liquids, it turns out to be the one which is the hardest to ignite by a hot surface. Nonetheless, in some cases, vehicular engine compartment temperatures can become high enough for gasoline to get ignited. When conducting HSIT tests, it is important to be cognizant of the probabilistic nature of the ignition problem.

在某些情况下，气体、蒸汽、液体喷雾、气溶胶和其他形式的可燃流体分散到大气中，可能会遇到热表面。在调查火灾时，可能有必要在这种情况下确定热表面是否是有效的点火源。该论文回顾了有关该主题的可用实验数据和结果，并给出了适当的建议。结果表明，与仅略微依赖于测试条件的自燃温度 (AIT) 不同，热表面着火温度 (HSIT) 高度依赖于测试环境条件。影响结果的主要变量是“封闭性”的程度。如果封闭程度不是极端，标准建议是可以假定热表面着火温度比 AIT 高 200°C。但对于明显封闭的条件，实际点火温度受燃料挥发性（与其闪点相关）的​​影响比其 AIT 值的影响更大。挥发性较高的燃料更难，而不是更容易从热表面点燃。由于汽油是常见的汽车用可燃液体中最易挥发的，因此它被证明是最难被热表面点燃的液体。尽管如此，在某些情况下，车辆发动机舱的温度可能会高到足以点燃汽油。在进行 HSIT 测试时，重要的是要认识到点火问题的概率性质。挥发性较高的燃料更难，而不是更容易从热表面点燃。由于汽油是常见的汽车用可燃液体中最易挥发的，因此它被证明是最难被热表面点燃的液体。尽管如此，在某些情况下，车辆发动机舱的温度可能会高到足以点燃汽油。在进行 HSIT 测试时，重要的是要认识到点火问题的概率性质。挥发性较高的燃料更难，而不是更容易从热表面点燃。由于汽油是常见的汽车用可燃液体中最易挥发的，因此它被证明是最难被热表面点燃的液体。尽管如此，在某些情况下，车辆发动机舱的温度可能会高到足以点燃汽油。在进行 HSIT 测试时，重要的是要认识到点火问题的概率性质。