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Harmonizing ventilation requirements for indoor lighter than air hazardous atmospheres

This paper compares the major concepts in ventilation requirements contained in API RP 500/505 and IEC 60079–10, specific to indoor, lighter than air, natural gas hazardous atmospheres. Engineering professionals rely on API 505 as the basis for area classifications. Previously, IEC and North American standards have been successfully adopted in the body of API 500/505 (79–10 Mod). However, the informative appendices of both standards covering ventilation calculations are not entirely consistent. This paper presents case studies for ventilation/classification and an attempt is made to harmonize ventilation calculations to offer further uniformity in global standards. This will be of interest to those involved with area classification activities, as the result may offer reduced mechanical ventilation demands, while maintaining equivalent levels of safety and reliability.