“Marginally explosible dusts (MEDs)” are a group of combustible dusts that are distinguished by relatively low volume-normalized maximum rate of pressure rise (K_St) and maximum explosion pressure (P_max) values. Earlier studies have suggested that dusts with K_St values less than 45 bar m/s in the laboratory-scale 20-L chamber would not explode in the 1-m³ chamber and therefore not on an industrial scale. Conversely, for some metallic dusts, significantly higher K_St values are generated in the 1-m³ chamber. Industries that handle MEDs continue to search for answers to the questions “are they explosible or not?” and “should we protect or not protect against potential explosions of these dusts?“. To answer these questions, four well-characterized materials namely, carbon black, oat grain flour, urea, and zinc were tested in the current study. These materials were selected because they exhibit different combustion behaviors and also cover a range of industries. Five ignition energies (i.e., 0.5, 1, 2.5, 5, and 10 kJ) were used in the 20-L chamber tests. The results show a clear case of overdriving (as a result of the high ignition energy density in the 20-L chamber) with respect to urea and carbon black dusts. Nevertheless, the urea dust is non-explosible. The data also suggests that the choice of test chamber to generate suitable explosion data is strongly dictated by the combustion path of MEDs. However, there are exceptions. The study also establishes the importance of both chemico-physical and thermal analyses to understanding the explosion behavior of MEDs. With reference to urea dust, a new definition for MEDs has been suggested as dusts having P_max < 3.0 bar(g), K_St < 20 bar m/s (in the 20-L chamber), MEC >1000 g/m³, MIE >1000 mJ, and MIT >600 °C. This work provides guidelines to industries that handle MEDs on the explosibility classification of these dusts, thus addressing the existing difficulty, and informing industry on the safety strategies required when handling this group of dusts.

“边缘爆炸性粉尘 (MED)”是一组可燃粉尘，其特点是相对较低的体积归一化最大压力上升速率 (K _St ) 和最大爆炸压力 (P _max ) 值。早期研究表明，在实验室规模的 20 L 室内， K _{St值小于 45 bar m/s 的粉尘不会在 1 m} ³室内爆炸，因此不会在工业规模上爆炸。相反，对于某些金属粉尘， 1-m ³室中会产生明显更高的 K _St值。处理 MED 的行业继续寻找“它们是否爆炸？”问题的答案。以及“我们是否应该防止这些粉尘潜在的爆炸？”。为了回答这些问题，本研究测试了四种特性良好的材料，即炭黑、燕麦粉、尿素和锌。选择这些材料是因为它们表现出不同的燃烧行为并且还涵盖了一系列行业。20 L 室测试中使用了五种点火能量（即0.5、1、2.5、5 和10 kJ）。结果显示，对于尿素和炭黑粉尘，存在明显的过度驱动情况（由于 20 升燃烧室中的高点火能量密度）。然而，尿素粉尘是不易爆炸的。数据还表明，用于生成合适爆炸数据的测试室的选择很大程度上取决于 MED 的燃烧路径。不过，也有例外。该研究还确立了化学物理和热分析对于理解 MED 爆炸行为的重要性。关于尿素粉尘，MED 的新定义被建议为 P _max < 3.0 bar(g)、K _St < 20 bar m/s（在 20 L 室中）、MEC >1000 g/m ^3的粉尘，MIE >1000 mJ，MIT >600 °C。这项工作为处理 MED 的行业提供了有关这些粉尘的爆炸性分类的指南，从而解决了现有的困难，并告知行业处理此类粉尘时所需的安全策略。