Storage of hazardous substances: The risks
There are a vast number of dangerous substances and products containing dangerous substances used in the workplace, varying in type, hazard, severity and the conditions under which they present a risk. The risk presented by substances is dependent on the substance itself and the quantity stored.
The precautions required to achieve a reasonable standard of control will vary but must take into account the properties of the substance to be stored. Different substances create very different risks because of their hazards. Storage conditions will require consideration of the physical and chemical properties, together with the health effects of the substances concerned.
Gas cylinders, because of their potential for danger, present specific problems.
Harm can be caused by:
- Explosion of the cylinder, particularly in fires
- Impacts causing violent release of compressed gas
- The release of the gas, which may:
- cause fire if the gas is flammable
- be asphyxiating if the release is into a confined space
- be toxic, e.g. carbon monoxide
- be corrosive, e.g. chlorine
- Injury caused by badly stored cylinders falling.
Gas cylinders should be stored:
- In a dry, safe place on a flat surface in the open air, or, if this cannot be done, in an adequately ventilated building or part of a building solely reserved for the purpose
- Away from external heat sources
- Away from sources of ignition and other flammable materials
- Securely, to prevent cylinders falling or being knocked over
- Away from vehicles such as fork-lift trucks.
Gas cylinders should also be clearly marked to show the contents and the hazards associated with their contents. The valve must be shut to stop contaminants entering. Gas cylinders should never be stored standing or lying in water.
The possibility of interactions between different substances, especially those which are incompatible, creating hazards must be considered.
Examples of incompatibles include:
- Acids which react with hypochlorites to generate chlorine gas
- Acids which react with cyanides to generate hydrogen cyanide gas
- Acids which react with alkalis to generate heat
- Acids which react with sulphides to generate hydrogen sulphide
- Nitric acid, which will react explosively with alcohol and other organic materials
- Oxidising agents, which should not be stored with organic materials.
The SDS of a substance should provide information on substances it is incompatible with. Incompatible substances should not be stored together and it is good practice to segregate acids from other substances.
Highly flammable liquids and gases
The storage of highly flammable liquids and gases should be carried out in a manner that:
- Minimises the risk of a fire or explosion occurring
- Avoids or minimises the potential risk of a spillage or release and mitigate the consequences of such incidents.
Highly flammable gases, liquids or liquefied gases should be stored in closed tanks, cylinders or containers constructed to an appropriate national or international standard. The storage area should be:
- Adequately separated from site boundaries, occupied buildings, process areas, fixed sources of ignition and other dangerous substances
- Be well ventilated to ensure that any such gases or vapours given off from a spill, leak or release are rapidly dispersed. Preferably, storage areas in the open air and if it is within a building, it should have adequate natural or mechanical ventilation
- Have adequate security arrangements to prevent any unauthorised access to dangerous substances and their associated storage equipment.
The contents of tanks, vessels and containers, should be clearly identified to make users or anyone who comes into contact with them aware of their contents and hazards. Cupboards, compounds and storerooms should also be clearly identified.
Dispensing or decanting should not be carried out in a storage area where they would create a risk of fire involving the stored materials.
The quantity of any highly flammable substance present within process vessels, pipelines, pumps, plant and any other associated equipment should be as small as is reasonably practicable.
The most common form of water pollution is pollution by oil. It is an offence to pollute water in the environment with oil.
The requirements for the storage of oil in containers which carry more than 200 litres are set out in the Control of Pollution (Oil Storage) (England) Regulations 2001. These regulations, which do not apply to waste oil or oil stored in a building or wholly underground, require:
- Secondary containment, a bund:
- with a capacity of not less than 110% of the container’s storage capacity
- positioned to minimise any risk of damage by impact, e.g. by fork-lift trucks
- with its base and walls impermeable to water and oil
- without its base and walls penetrated by any valve, pipe or other opening used for draining the system
- with the base or walls, where they are penetrated by any fill pipe, or draw off pipe, adequately sealed to prevent oil escaping from the system
- Any valve, filter, sight gauge, vent pipe, etc. to be situated within the secondary containment system
- Fill pipes, not within the secondary containment system, to have a drip tray to catch any oil spilled when the container is being filled with oil.
The regulations also include requirements for the storage of oil in fixed tanks, both above ground and underground, which include particular requirements for ensuring that fill, draw-off and overflow pipes are not damaged, and that the tanks are fitted with automatic overfill protection devices.
Storing large quantities of substances
The risk from the storage of dangerous substances is dependent on the amount of dangerous substance present. The following factors should be considered.
- Storage buildings and outdoor storage compounds for dangerous substances are subject to controls under building legislation. In England and Wales, Approved Document B under the Building Regulations 2010 set out standards for fire resistance and compartment size for industrial or storage buildings.
- Storage buildings and outdoor storage compounds for dangerous substances are subject to controls under planning legislation. The Planning (Hazardous Substances) Regulations 1992, as amended in 2009 and 2010, and the Town and Country Planning (Hazardous Substances) (Scotland) Regulations 1993, as amended in 2009, apply to facilities where controlled hazardous substances are stored in quantities above a specified minimum.
- In premises where certain dangerous substances are present above specified thresholds, the Control of Major Accident Hazards Regulations 2015 (COMAH), require operators to take measures to prevent major accidents. The steps include the storage of the dangerous substances.
- If the COMAH Regulations apply, the risk assessment has to be very detailed, and cover storage facilities.
Procedures for dealing with emergencies related to the hazardous substances being stored need to be developed. Consideration needs to be given to the range of possible events, including:
- Releases, e.g. leakages or spillages.
The following factors must also be taken into account.
- The nature and quantities of the dangerous substances stored.
- The location and design of the storage facility.
- The people, both on and off the site, who may be affected.
Safe systems of work for dealing with spillages and leakages should be put in place and will depend on the nature of the substance involved.
SDSs will give details of any specific action to be taken for dealing with spillages. These need to be available for all the substances stored on site.
Employers must provide adequate information, instruction and training to employees on the:
- Risks presented by the substances to be stored
- Procedures for safe storage of hazardous substances
- Procedures for fires involving stored hazardous substances
- Procedures for spillages, leakages and other releases of hazardous substances
- Procedures for other incidents involving the release of stored materials.