Hazardous Area Classification
Hazardous area classification is the process of identifying locations where flammable gas, vapour, mist or combustible dust may be present in quantities sufficient to form an explosive atmosphere, and grading them by the likelihood and duration of that presence. Under IEC 60079-10-1 for gases and IEC 60079-10-2 for dusts, gas areas are divided into Zone 0, 1 and 2 and dust areas into Zone 20, 21 and 22; North American practice under NEC Articles 500 and 505 uses Class and Division or Zone systems. The classification determines which electrical and mechanical equipment may be installed. Ex equipment is selected by Equipment Protection Level (EPL), gas group (IIA, IIB, IIC), temperature class (T1 to T6) and protection concept, such as flameproof Ex d, increased safety Ex e or intrinsic safety Ex i. API RP 505 provides guidance for petroleum facilities.
Examples
- Zone 1 classification around a compressor seal area
- Zone 2 area around flanged piping in an open process plant
- Zone 21 classification inside a powder handling area