DSEAR challenges
in air, is likely to occur in normal operation occasionally. In most circumstances, the extent can be defined by evaluating sources of release in relation to the environment, causing explosive dust atmospheres. The extent is as follows: • the inside of some dust handling equipment in which an explosive dust atmosphere is likely to occur
• the area outside the equipment, formed by a primary grade of release, depends on several dust parameters such as dust amounts, flow rate, particle size and product moisture content – this zone should remain limited
Consideration needs to be given to the source of release, taking into account the conditions leading to release in order to determine the appropriate extent of the zone. For areas outside buildings (open air), the boundary of Zone 21 can be altered due to weather effects such as wind or rain.
Zone 22
A place in which an explosive dust atmosphere in the form of a cloud of dust in air is not likely to occur in normal operation, but if it does, will persist for a short period only. In most circumstances, the extent can be defined by evaluating secondary grade sources of release in relation to the environment causing the explosive dust atmospheres. The extent of an area formed by a secondary grade source of release depends on several dust parameters such as dust amounts, flow rate, particle size and product moisture content. Consideration needs to be given to the
source of release, taking into account the conditions leading to release, in order to determine the appropriate extent of the zone. For areas outside buildings (open air), the boundary of Zone 22 can be altered due to weather effects such as wind and rain.
Equipment in hazardous areas
Special precautions need to be taken in hazardous areas to prevent equipment from being a source of ignition. Where an explosive atmosphere is likely to occur, reliance is placed on using equipment with a low probability of creating an ignition source. Where the likelihood of an explosive atmosphere occurring is reduced, equipment constructed to a less rigorous standard may be used. Equipment is categorised as one, two or three depending on the zone in which it is intended to be used. Part two of this series will look in more depth at the risks faced by businesses that are storing, handling and using hazardous materials as
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part of their daily business operation, risk reduction factors and case studies where DSEAR risk assessments have not been carried out, resulting in fires and explosions
Marcus Rees is fire risk consultant and lead DSEAR assessor at the FPA. For more information, view page 5
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