Mobile Phones in Category 3 Explosive Gas Atmospheres

The risk associated with using a mobile phone in a Category 3 (Zone 2) Explosive Gas Atmosphere is evaluated. Experimental trials were performed on a representative sample of commercial grade mobile phones using the guidelines provided in The Instrumentation, Systems, and Automation Society\´s ISA-RP12.12.03-2002 "Recommended Practice for Portable Electronic Products Suitable for Use in Class I and II, Division 2, Class I Zone 2 and Class III, Division 1 and 2 Hazardous (Classified) Locations". The ignition risks are subsequently classified according to a framework ranking system for ignition sources developed by Rew and Spenser (1997). The results are used to construct a probability model that estimates the risk of a mobile phone igniting a flammable atmosphere in a Category 3 explosive gas atmosphere. The IEC or ATEX has not issued an equivelant standard to ISA-RP12.12.03-2002 for portable electronic products. The development of a harmonized standard is currently under review. While the ISA Standard references the terms Class I and II, Division 2, Class I Zone 2 and Class III, Division 1 and 2 Hazardous (Classified) Locations", these terms are essentially equivalent to the definitions used by the IEC and/or CENELEC for Category 3, Zone 2 and Zone 22 locations. Not all the mobile phones evaluated met the ISA-RP12.12.03-2002 requirements for a PEP 2 (Portable Electronic Product) device and therefore could not be considered "incapable of causing an ignition under normal operating conditions" as per the PEP definition. Additional testing and analysis of the high risk mobile phone components indicated a very low probability of ignition even under ideal conditions. A Monte Carlo simulation of the probability model estimated the odds of a mobile phone causing a fire or explosion in a Category 3 -Zone 2 Explosive Gas Atmosphere as being 1.16E-06; or one in a million.