Hazardous Area Classification Due to Combustible Dust Atmospheres and Layers: Avoiding Common Mistakes

Abstract

In areas and workplaces where combustible dusts are produced, handled or stored, Hazardous Area Classification is required to assess the likelihood of formation of a dust explosive atmosphere. The resulting dust zoning is of paramount importance in deciding the type and protection modes of electrical and non-electrical apparatuses to install in those areas. Dust zoning is a widespread and well-known technique, covered by dedicated technical Standards such as IEC 60079-10-2 and NFPA 499. As such, it also represents the first step for a dust explosion risk assessment, therefore its quality and completeness are of the utmost importance in order to achieve a high-value, robust explosion risk management. The behavior of fires and explosions from dust clouds or layers is strictly dependent on the chemical-physical characteristics of the dust: the first section of this paper shall analyze those characteristics, and how their variations affect the classification of areas. After this overview, the paper shall illustrate the most common misconceptions and mistakes that can be encountered in Hazardous Area Classifications and provide insights and suggestions on how to avoid them.