The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) require employers to control the risks to safety from fire, explosions and substances corrosive to metals.
There is a legal requirement to carry out a hazardous area study or assessment and to record the results using zones.
An explosive atmosphere is a mixture of air and dangerous substances with the potential to catch fire or explode.The dangerous substances can burn or explode if an ignition source is present and include flammable gases such as propane and hydrogen, flammable liquids and solvents such as paints and thinners, dusts from foodstuffs like flour or from woodworking, pressurised gases like oxygen and nitrogen, and substances like hydrochloric acid which can burn through metal. When acids attack metals, hydrogen is often given off which is a flammable gas.
DSEAR assessments are required for dangerous substances that are stored, used or are created through work processes. The assessment should begin with a tour of the site to determine if hazardous areas exist and to ensure all relevant areas are included.
The assessment then goes on to consider the following criteria:
• Hazardous properties of dangerous substances such as boiling point, flash point and flammability limits
• Quantities of dangerous substances involved
• Work processes involving the substances
• The temperatures and pressures at which the substances are being handled or stored
• The containment and controls provided to prevent gases, liquids, vapours or dusts escaping to the workplace atmosphere
• Ventilation types and levels.
Depending on the findings this far, hazardous area zones may need to be calculated and drawn.
The zones are based on the frequency and persistence of the potentially explosive atmosphere. These zones help to determine the controls that are required to manage the source of ignition that could be present in the area. They also determine the equipment that is allowed to be in the area; any equipment that has a risk of generating explosion must be eliminated from the area.
These zones and the DSEAR risk assessment must be made readily available to all employees working in the areas, and also for the emergency services should an explosion occur.
Where the risk cannot be eliminated, DSEAR requires control measures to be applied in the following priority order:
• Reduce the quantity of dangerous substances to a minimum
• Avoid or minimise releases of dangerous substances
• Control releases of dangerous substances at source
• Prevent the formation of a dangerous atmosphere
• Collect, contain and remove any releases to a safe place (for example, through ventilation)
• Avoid ignition sources;
• Avoid adverse conditions (for example, exceeding the limits of temperature or control settings) that could lead to danger
• Keep incompatible substances apart.