What is an explosive hazardous area?

Explosives hazardous areas occur where flammable liquids, vapors, gases or combustible dusts are likely to occur in quantities sufficient to cause a fire or explosion. Often, these atmospheres are created where gas, vapors, dusts and liquids are in contact with oxygen. Hazardous areas are divided into zones, where the probability of a hazardous atmosphere being present governs the explosion risk. Some areas are more hazardous than others, since it is more likely that there are gasses present. There are explosive gas atmospheres, explosive dust atmospheres, and the explosive atmospheres which may exist in coal mines.