In the many industrial processes where flammable materials are handled, any leak or spillage may give rise to an explosive atmosphere. To protect both personnel and plant, precautions must be taken to ensure that this atmosphere cannot be ignited. The areas at risk are known as ‘hazardous areas’ and the materials that are commonly involved include crude oil and its derivatives, natural and man-made process gases, alcohols, dusts, carbon dust, flour, starch, grain & fibres.