That's classified

The basic characteristic of oil and petrochemical industry processes is the use of flammable substances at high pressures and flows. Despite the strict requirements enforced to build process equipment that will be used in these industries, the high risk of accidents involving explosions and fires draws the attention of researchers because of the number of victims, material losses, and environmental damages. Locations where an explosive atmosphere may be formed are called "classified areas." Once these areas are identified, the technical specifications for electrical and electronic equipment and the development of specific operational procedures to ensure safety at work in these areas can be written and enforced.