Part 1 of this blog series introduced the concept of intrinsic safety. Part 2 describes the characterization of hazardous environments with respect to intrinsically safe circuit design of electronic devices.
Internationally, the International Electrotechnical Commission (IEC) is considered to be a benchmark in the definition of explosive atmospheres and certification of electrical equipment for explosive atmospheres via its IECEx standards. Additionally, various countries impose their own standards and requirements in defining explosive atmospheres. The ATEX (ATmosphere EXplosibles) standard is applicable to thirteen countries within the European Union.
In the US, regulatory bodies such as the Occupational Safety and Health Administration (OSHA) and National Electrical Code (NEC) have established definitions that classify locations which exhibit potentially dangerous conditions to the degree of hazard presented. In hazardous locations, specially designed equipment and special installation techniques must be used to protect against the explosive and flammable potential of these substances. Similarly, in Canada, the Canadian Electrical Code (CEC) defines hazardous areas.
Each standard/classification has slightly different requirements, which makes it critical to identify all required environments and geographies prior to design. Although these standards are harmonized, it is possible to design a product that does not meet the intended use environment without a major redesign.
