Abstract
In process industries involving the generation, handling, or storage of combustible dusts, hazardous area classification is a fundamental activity for assessing the risk of explosive atmosphere formation. This classification, governed by international technical standards such as IEC 60079-10-2 and NFPA 499, provides the methodological basis for implementing effective protection measures in compliance with industrial safety requirements. This paper analyzes complex scenarios characterized by the presence of hybrid mixtures—i.e., potentially explosive atmospheres consisting simultaneously of flammable gases/vapors and combustible dusts. In particular, it examines operating conditions in which, during the manual loading of reactors containing flammable solvents, the introduction of powders by the operator can generate hybrid mixtures with high explosive potential. Several different options will be examined and discussed, showing benefits and disadvantages for each configuration. The main parameters that will be used in the discussion will be the ones related to the flammability and ignitability of gases / vapors and combustible dusts. In conclusion, the document provides operational recommendations and technical insights aimed at mitigating explosion risks in environments characterized by high process complexity, promoting a risk management approach aligned with the principles of safety engineering.
