As a rule, for explosions to happen in atmospheric
air, three factors have to be present at the same
– flammable material
– oxygen (air)
– source of ignition In production and work places, hazardous areas can develop wherever the first two preconditions for an explosion are fulfilled.
Typical hazardous areas form in chemical factories, refineries, enamelling plants, paint workshops, cleaning equipment, mills and stores for milled products and other combustible dusts, in tank facilities and loading areas for flammable gases, liquids and solids. The first two preconditions - the flammable material and air - must be present in justified quantities between LFL and UFL (Lower Flammable Limit and Upper Flammable Limit) to form an explosive atmosphere. The statutory definitions of explosion protection - derived from the health and safety at work regulations - are in relation to workplaces. For this reason, explosion protection is generally limited to description of reactions with oxygen in the air. Oxidation reactions normally involve increasements in heat and pressure and therefore fulfil the criteria of an explosion.