Flameless venting is a sort of dual mitigation technique allowing, in principle, to vent a process vessel inside a building where people are working without transmitting a flame outside the protected vessel. Existing devices are an assembly of a vent panel and a metal filter so that the exploding cloud and the flame front is forced to go through the filter. Within the frame of ATEX Directive, those systems need to be certified. To do so a standard (NF EN 16009) has been issued describing which criteria need to be verified/measured. Among them, the “efficiency” factor as defined earlier for standard vents. This implies that flameless venting systems are basically considered as vents. But is it really so? This question is discussed on the basis of experimental results and some implications on the practical use and certification process are drawn. The practical experience of INERIS in testing such systems is presented in this paper. Schematically, with a flameless vent the pressure is discharged but not the flame so that combustion is proceeding to a much longer extent inside the vessel than with a classical vent so that the physics of the explosion is different. In particular it is shown that besides the problem of the unloading of the confined explosion, there is a highly complicated fluid mechanics problem of a fluid-particle flow passing through a porous media (the flameless device grids arrangement in the filter), which passing surface is progressively reduced. To characterize Flameless venting the problem can be addressed sequentially, considering separately the vent panel and the flameless mesh. A model is proposed to estimate the overall venting efficiency of the flameless vent. However, it does not address the flame quenching issue, which is a different problem of heat exchange between the devices and the evacuated burnt products.

无焰泄放是一种双重缓解技术，原则上允许在人们工作的建筑物内对处理容器进行泄放，而不会将火焰传播到受保护容器外。现有的设备是一个通风板和一个金属过滤器的组合，以便爆炸云和火焰前沿被迫通过过滤器。在 ATEX 指令的框架内，这些系统需要经过认证。为此，已发布标准 (NF EN 16009)，描述需要验证/测量哪些标准。其中，前面定义的标准通风口的“效率”因素。这意味着无焰通风系统基本上被视为通风口。但真的是这样吗？这个问题是在实验结果的基础上讨论的，并得出了对实际使用和认证过程的一些影响。本文介绍了 INERIS 在测试此类系统方面的实践经验。从原理上讲，使用无焰泄放时压力会释放，但不会释放火焰，因此与经典泄放相比，容器内的燃烧进行的时间长得多，因此爆炸的物理原理是不同的。尤其表明，除了密闭爆炸的卸荷问题外，还有一个高度复杂的流体力学问题，即流体粒子流通过多孔介质（过滤器中的无焰装置网格排列），其通过表面逐渐减少。为了表征无焰通风，可以依次解决问题，分别考虑通风面板和无焰网。提出了一种模型来估计无焰通风口的整体通风效率。