Many organisations need to store substances that are classified as hazardous to health, sometimes in substantial quantities. As discussed previously, several sets of Regulations may apply, depending on the exact nature of the substance being store, but in nearly every case, the Control of Substances Hazardous to Health Regulations 2002 (or COSHH Regulations) will apply. However, consideration needs to be given to the full range of hazards that may be present, including issues such as compatibility with other materials, reaction with air or water, etc. Many aspects of the safe storage of substances hazardous to health rely on common sense and part of the purpose of the COSHH risk assessment is to formalise the application of this common sense.
Storage of gases
Gases are usually stored under pressure inside metal gas bottles. These bottles can vary in size from a few millilitres up to several tonnes. The gas bottles, and associated pipe work, must be colour coded and/or labelled for identification purposes as required by either various pieces of specific legislation (which are outlined in Schedule 7 of the COSHH Regulations) or by Regulation 12(5) of the COSHH Regulations (a requirement that was new in the 2002 Regulations). Similar rules apply to pipe work systems used for the storage and transfer of liquids and even solids.
Where incompatible gases are being used on a site, there must be a safe system of work in operation that negates the possibility of the accidental mixing of these gases. In the case of hydrogen and oxygen, these gases have different screw threads on their fittings to prevent accidental connection of the wrong gas to the wrong part of the system (this system is also seen on oxy-acetylene welding/cutting equipment).
Gas cylinders, and the associated supply pipe work, need to be adequately protected from accidental damage (such as from vehicle movements). They may also need to be protected from heat, including heat build up from sunlight.
Storage of liquids
Bulk storage
Bulk storage of liquids generally takes place is designated bulk storage tanks. These tanks are usually bunded, to contain accidental releases of materials. The tanks are usually filled from a delivery tanker. It is essential that the right material is unloaded into the right tank. There have been a number of serious industrial accidents when tanks have been charged with the wrong chemical. Once such incident is described later in the section dealing with acids/hypochlorite solutions and is described in more detail below.
Small/medium scale storage
Small and medium scale storage of solid hazardous substances generally involves intermediate bulk containers (IBCs), drums or bottles. The size may vary from a few grams up to about 1200 Kg.
Storage of oil
It is not uncommon for water to be polluted by 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 (such as a bund):
- with a capacity of not less than 110 per cent 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.
Storage of solid materials
Bulk storage
Bulk storage of solid materials may take place in several ways:
- Loose, but in defined locations in a yard (e.g. granite or asphalt blocks)
- In large open access bins (sand, etc.)
- In silos (e.g. flour, various process chemicals)
- In “big bags” which generally hold between one and three tonnes (a range of process chemicals)
If powdery or friable materials are stored loosely, the effect of dispersal by wind, leading to airborne contamination, must be considered.
Small/medium scale storage
Small and medium scale storage of solid hazardous substances generally involves bags, sack, drums or bottles. The size may vary from a few grams up to about 250 Kg. Materials may also be stored in roll form, such as in the case of glass fibre, or rolls of various fabrics impregnated with resins, etc.
Storage of incompatible or reactive materials
Where there is a risk of accidentally mixing materials that are incompatible, there is a duty to ensure that all reasonably practicable measures are taken to prevent this from occurring. This will include, amongst other things, the introduction and maintenance of a safe system of work designed to prevent mixing. Deliveries, including accompanying paperwork, should be checked carefully and all deliveries and transfers should be supervised adequately.
Acids/bases
Acids and bases must be stored separately as significant heat (of neutralisation) may be generated when these materials are mixed. The storage arrangements for these materials should ensure that they cannot be mixed accidentally, even in the event of spillage. Ideally, these materials should be stored in separate, bunded locations.
Acids/hypochlorite
Acids and hypochlorite mixtures should be stored separately as toxic chlorine gas is generated when these materials are mixed. The storage arrangements for these materials should ensure that they cannot be mixed accidentally, even in the event of spillage. Unfortunately, in premises with swimming pools (where hypochlorite solutions are often used as part of the water treatment) these materials are often stored close to each other. It is recommended that containers of these two substances are bunded separately to prevent mixing after a spillage has occurred.
Case study: - The danger from the accidental mixing of acids and hypochlorites was shown in the following case study:
In September 2002, a lorry driver from AE Costins Limited delivered an IBC of hypochlorite solution to site on behalf of the supplier and distributor (Tennants Distribution Limited). The lorry driver then accidentally connected the IBC to a hydrochloric acid bulk storage tank instead of the hypochlorite bulk storage tank. When the hypochlorite was pumped into the wrong tank the two chemicals reacted, generating a cloud of chlorine gas. 26 employees were taken to hospital for examination, though only one was detained overnight. This accident was blamed onto the inadequate training of the lorry driver and the failure of Tennants Distribution Limited to ensure that driver of vehicle contracted to the Company to and transfer sodium hypochlorite solution were competent to do so. Tennants were fined £12,000, with costs of about £5,500.
Acids/(poly)sulphides
Acids and sulphides (including polysulphides) must be stored separately as toxic hydrogen sulphide gas is generated when these materials are mixed. In July 2001, a load of waste alkali that was contaminated with polysulphides reacted with some waste acids at Park Environmental Services Limited, liberating hydrogen sulphide gas. One employee was overcome by the gas and was further injured by falling down steps. Although often underrated as a toxic gas, hydrogen sulphide is more toxic than hydrogen cyanide. The Company was fined a quarter of a million pounds under S2 (1) of the Health and Safety at Work Etc Act 1974, with costs of about £20,000.
Fortunately, its smell is unpleasantly noticeable well below its toxic level. The storage arrangements for these materials should ensure that they cannot be mixed accidentally, even in the event of spillage.
Acids/cyanides
Acids and cyanides must be stored separately as toxic hydrogen cyanide (cyanide gas) is generated when these materials are mixed. The storage arrangements for these materials should ensure that they cannot be mixed accidentally, even in the event of spillage. More is said on the storage of cyanides in the section on highly toxic substances (below).
Oxidising agents/organic materials
Oxidising agents include a wide range of commonly used substances, including peroxides (such as methyl ethyl ketone peroxide, or MEKP, used in the manufacture of glass reinforced plastics, or GRPs, and chromic acid (used in the certain electroplating processes). Fires may be initiated by the action of oxidising agents on organic materials. This may include the organic materials often associated with packaging and storage, such as paper, cardboard and wooden pallets. Naturally, consideration needs to be given to the safe storage of oxidising agents. The area should be clearly identified and organic materials (including packaging and process chemicals) must be excluded from this area.
Materials that react with water
Many substances react violently with water. Some produce explosive gases, such as the release of acetylene from the reaction of calcium carbide with water, or the release of hydrogen from the reaction of alkali metals (such as potassium or sodium) with water. Sodium also generated enough heat to ignite the released hydrogen). Other materials react violently with water to generate heat, known as the heat of dilution (such as in cases of pearl caustic soda, concentrated sulphuric acid, oleum, etc.). The dilution of these materials needs to done correctly, usually with stirring and cooling as well as consideration to the order of addition, etc.
Materials that react with air
Some materials (such as Raney nickel catalysts) react violently (or even pyrophorically) with air. Typically, these materials are stored under water, such as in the form of a slurry.
Storage of highly toxic substances
With highly toxic substances, it is recommended that these are stored in a secure location, such as a locked storage area. It is also recommended that an inventory of stored materials is maintained, including records of usage.
As with all substances hazardous to health, consideration must be given to reducing the amount of these substances used and/or stored as well as giving consideration to the use of these materials at all. Regulation 7(2) of COSHH 2002 creates a duty to consider safer alternatives.
Storage of waste materials
Consideration needs to be given to the hazardous nature of stored waste materials. Consideration needs to be given to the toxic, corrosive or otherwise harmful nature of the substance, as well as any incompatibilities.
Application of COSHH to storage
As stated at the start of the first article, COSHH applies as much to the storage of substances hazardous to health as it does to their use. The COSHH Regulations require employers to prevent exposure to hazardous substances to both employees and non-employees where it is reasonably practicable to do so. Where it is not reasonably practicable to avoid exposure, then exposure must be adequately controlled. COSHH assessments must consider the storage of substances as well as their use.
Michael Ellerby
LLB BSc CMIOSH MIIRSM MIFSM CChem MRSC CSci
Director
LRB Consulting Limited
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