Optimization of Explosive Atmospheres Hazardous Area Classification in Pharmaceutical Liquid Manufacturing Using a Semi‐Empirical Ventilation‐Based Approach

Abstract Explosive ATmospheres (ATEX) zoning in process industries is commonly based on standards such as International Electrotechnical Commission (IEC) 60079‐10‐1. However, when ventilation performance is not quantitatively evaluated, their practical application may result in conservative estimations of hazardous volumes, particularly in highly ventilated environments. A semi‐empirical methodology integrating evaporation rate modeling and ventilation performance is proposed to quantify vapor generation and determine the minimum ventilation rate required to maintain concentrations below 25% of the lower explosive limit. The approach is applied to a pharmaceutical facility using ethanol with an air exchange rate of 25 vol h −1 . The vapor generation rate is estimated at 2.01 m 3 h −1 , leading to a critical ventilation rate of about 244 m 3 h −1 . For the studied configuration (170 m 3 ), the actual ventilation rate exceeds this threshold, with a safety factor (Qreal/Qmin) of approximately 17.4. The results indicate that large‐scale vapor accumulation is unlikely under the studied ventilation conditions, although localized transient flammable atmospheres may still occur near potential release sources. The results show that explicitly accounting for ventilation performance allows a reduction in the conservatism of ATEX zoning while maintaining an adequate safety factor. The proposed methodology provides a practical framework for risk‐informed hazardous area classification in ventilated industrial environments.