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On the Classification of Flammable Gases, Vapors and Dusts.
Proceedings of the International Symposium on the Explosion Hazard Classification of Vapors, Gases, and Dusts, National Materials Advisory Board, Publication NMAB-447 1987:25-39
Classifying the explosive hazards of flammable gases, vapors, and dusts was discussed. When attempting to devise a classification scheme for flammable substances, the ease of ignition and the violence of the explosion must be considered. Choosing parameters for classifying the explosive potential of flammable substances was discussed. The general requirements for explosion parameters used in classification schemes were listed. The maximum experimental safety gap (MESG) as a basis for classifying the explosibility potential of gases and vapors was discussed. The MESG can be defined as the transmissibility of a confined explosion through a narrow gap to the outside environment. Because MESGs can only be determined empirically, they are arbitrary in nature. It was noted that because of its arbitrary nature it is considered questionable to use the MESG in practical applications such as designing explosionproof enclosures. Relating the MESG to the properties of a burning gas mixture was discussed. To utilize the MESG to classify flammable gases, it was noted that an entire spectrum of MESG values must be obtained for each gas, a time consuming and expensive process. Classifying dusts according to their explosive potential was considered. In the United States ignition sensitivity and explosion severity of dusts are defined in terms of their minimum ignition energy, explosible dust concentration, and ignition temperature, maximum ignition temperature, and rate of pressure increase, determined experimentally. It was noted that very little is known about the mechanism for propagating a dust flame. Experience has shown that dust/air mixtures can propagate flames and that the flame propagation rate is strongly influenced by turbulence.
Explosive-dusts; Combustible-gases; Laboratory-testing; Fire-hazards; Industrial-safety; Explosion-prevention;
Proceedings of the International Symposium on the Explosion Hazard Classification of Vapors, Gases, and Dusts, National Materials Advisory Board, Publication NMAB-447
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division