Rooms and outdoor sites with particular risk of fire, particularly work locations exposed to fire hazards. Those present the danger for substances highly flammable under the conditions of site and operation such as dust and/or fibres in hazardous quantities to approach electrical equipment in a way that turns elevated temperatures at such equipment into fire hazards. This includes work, drying and storage rooms; storerooms for hay, straw, jute and flax as well as corresponding outdoor storage areas, e.g. in paper, textile or wood working plants. Highly flammable in the context of this standard refers to substances which remain on fire or smouldering after 10 seconds of contact with the flame of a match, but do not trigger explosion hazards in the atmosphere. These substances include e.g. straw, hay, straw dust, wood shavings, loose wood wool, magnesium flakes, brushwood, loose paper, cotton and spun rayon fibres.