All work areas with possible formation at any time of explosive atmospheres due to the presence of flammable gases or vapors, combustible dusts, must be studied and divided according to their category.

• Zone 0: Work areas where the explosive atmosphere is permanently present.

• Zone 1: Work areas susceptible to explosion under normal working conditions.

• Zone 2: Work zones in which the presence and possibility of an explosion is unlikely and for short periods.

• Zone 20: Work zones in which the Explosive Atmosphere forms in the form of a cloud of combustible dust in the air present or permanently.

• Zone 21: Work areas where occasional formation is possible under normal conditions in the form of a cloud of combustible dust in the air.

• Zone 22: Work areas in which the explosion or formation of explosive atmospheres is unlikely under normal conditions.

Common jobs in which there is the possibility of being an Atex zone are explosive liquid transfer areas, paint booths, solvent warehouses, chemical industry, cereals, mills, coal treatment plants, fertilizers, etc.