Hazardous chemicals should be stored in the smallest practical quantity, in their original labelled containers, in a cool, dry, ventilated and secure place, with spills contained and incompatible products kept apart. Flammable liquids belong in a fire-resisting cabinet or a dedicated store, away from heat and escape routes. The mistakes HSE guidance keeps returning to rarely involve exotic substances. They involve ordinary products stored badly: bleach on the same shelf as an acid descaler, solvent decanted into an unlabelled drinks bottle, thinners beside a heater, and drums on a bare floor with nothing to catch a leak.
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This guide covers the law on chemical storage, which products must never share a shelf, where and how to store them, limits for flammable liquids, labelling, bunding and spill kits, disposal, training, and a monthly checklist for your chemical store.
What does the law say about storing hazardous chemicals?
There is no single “chemical storage regulation”. Two sets of regulations name storage directly, and HSE guidance sets out good practice.
COSHH. Regulation 7 of the Control of Substances Hazardous to Health Regulations 2002 requires employers to prevent or adequately control exposure. Regulation 7(4) says the control measures must include “arrangements for the safe handling, storage and transport of substances hazardous to health, and of waste containing such substances, at the workplace”. It also requires the quantity of hazardous substances at the workplace to be kept to the minimum the work needs. Storage is part of your COSHH assessment, not a separate housekeeping task. Our guide to the COSHH Regulations and employer duties covers the other regulations.
DSEAR. For substances that can burn or explode, the Dangerous Substances and Explosive Atmospheres Regulations 2002 go further. Regulation 5 requires the risk assessment to consider the risk of substances in combination and “the arrangements for the safe handling, storage and transport” of dangerous substances. Regulation 6 lists control measures in priority order, starting with “the reduction of the quantity of dangerous substances to a minimum” and including “the segregation of incompatible dangerous substances”.
Labelling and signs. COSHH regulation 12 and DSEAR regulation 10 require the contents of containers, and their hazards, to be clearly identifiable. The Health and Safety (Safety Signs and Signals) Regulations 1996 add that containers used at work for hazardous chemicals, and containers used to store them, must carry the relevant hazard pictograms, and that rooms used to store significant quantities must normally be marked with a warning sign.
Guidance. The key HSE documents are HSG51 The storage of flammable liquids in containers (third edition, 2015), HSG71 Chemical warehousing (2009) and the COSHH essentials sheet SR24 Storing chemical products (small scale). The Approved Codes of Practice are L5 for COSHH (sixth edition, 2013) and L138 for DSEAR (second edition, 2013).
What are the dangers of storing chemicals incorrectly?
Poor storage creates four kinds of harm.
- Fire. Flammable liquids give off vapour that is heavier than air and collects at low level. HSG51 warns that if it ignites there, the flame is likely to flash back to the liquid it came from. Oxidising substances make things worse: HSG71 says oxidising agents “will greatly increase the severity of a flammable liquid fire”.
- Toxic gas. Two products can react if they leak or are mixed. Bleach and acid release chlorine gas.
- Burns and poisoning. A corrosive liquid dropped from a high shelf can splash into someone’s face. A chemical decanted into a drinks bottle can be drunk by mistake.
- Pollution. A leak that reaches a surface water drain can reach a river. Firefighting water can carry chemicals off site too.
The first thing to catch fire is often not the chemical. HSG71 says that in many cases it is packaging, pallets or rubbish, ignited by a discarded cigarette or a spark from poorly controlled hot work. Spare batteries are another stored fire risk; see whether lithium-ion batteries are a fire risk.
Which chemicals should never be stored together?
Segregation means keeping incompatible substances apart, by distance or a barrier, so a leak from one cannot reach the other. SR24 gives a simple starting rule: keep apart solid and liquid products, flammable and non-flammable liquids, acids and alkalis, and wastes. The pairings below, from HSE and UK Health Security Agency (UKHSA) guidance, are examples, not a complete list.
| Never store together | What can happen | Source |
|---|---|---|
| Bleach (sodium hypochlorite) and acidic products, such as acid descalers and limescale removers | Chlorine gas, which irritates the eyes, throat and lungs and at high concentrations can be fatal | UKHSA; HSE HSG71 |
| Bleach and ammonia-containing cleaners | Chloramines, which UKHSA describes as highly irritating to the respiratory tract | UKHSA |
| Acids and alkalis | The reaction generates heat | HSE HSG71; HSE SR24 |
| Acids and cyanides | Hydrogen cyanide gas | HSE HSG71 |
| Acids and sulphides | Hydrogen sulphide gas | HSE HSG71 |
| Oxidising substances and flammable materials | Oxidisers can help other materials burn rapidly even if air is excluded, and greatly increase the severity of a fire | HSE HSG71 |
| Substances dangerous when wet, such as calcium carbide, sodium, and magnesium or aluminium powder, and water | They react with water and give off flammable gas | HSE HSG71 |
| Flammable liquids and corrosives or oxidisers in the same cabinet | Corrosives can attack containers or the cabinet; oxidisers raise the fire risk | HSE HSG51 |
Bleach and acid is the pairing you are most likely to find in an ordinary cleaning cupboard. UKHSA’s sodium hypochlorite guidance says minor exposures, “such as those usually seen when cleaning products have been mixed together”, cause burning eyes and throat, coughing and a sore throat, and more substantial exposure can cause breathing difficulties. A cleaner’s cupboard with bleach and a limescale remover on one shelf is a segregation problem.
Hazard pictograms help you sort products into groups; our guide to COSHH symbols and hazard pictograms explains each one. But pictograms do not show every incompatibility. HSG71 warns that substances its own segregation table shows as compatible “may react together”, particularly corrosives, so always check the safety data sheet. Section 7.2 covers “Conditions for safe storage, including any incompatibilities” and section 10.5 lists incompatible materials.
Where should hazardous chemicals be stored?
SR24 asks for a “cool, dry, dark, ventilated place”, arranged “in such a way as to retain any spills”, holding only the amount you need. A good chemical store is:
- Ventilated at high and low level. Because flammable vapours are heavier than air, HSG51 recommends permanent openings, such as louvres or airbricks, at both levels.
- Away from heat and sunlight. HSG51 warns about containers warming in direct sunlight or under roof lights, or touching hot pipes.
- Off escape routes. HSG51 says flammable liquid cabinets should be in areas that “do not jeopardise the means of escape”. Never store chemicals in corridors or beside fire exits.
- Heavy items and corrosives low. SR24 says to store heavier items and corrosive chemicals on lower shelves. Nobody should lift corrosive liquid down from above head height.
- Labels facing forwards, where they cannot be damaged, as SR24 advises.
- Floored to suit the contents. HSG71 notes that many acids attack concrete and solvents attack bitumen. A sill across the doorway, typically about 150 mm high, keeps leaks in.
- Locked. SR24 says only authorised, appropriately trained people should have access.
- Signed on or near the door where it holds significant quantities.
- Free of food and drink. Safety data sheets advise not to eat, drink or smoke in work areas.
Gas cylinders need their own arrangements. HSG71 notes that leaks disperse more readily in the open air, and says liquefied gas cylinders should be stored upright and secured against toppling.
How should flammable liquids be stored at work?
Flammable liquids fall under both COSHH and DSEAR, and HSG51 is the main guidance. Its approach rests on four points.
Keep only what you need in the work area. HSG51 accepts that many jobs need flammable liquids close at hand. A limited quantity, in closed containers, may be kept in fire-resisting cabinets or bins designed to retain spills, holding 110% of the largest container normally stored in them. HSG51 calls for 30 minutes’ fire integrity and close-fitting doors.
Treat the inside of the cabinet as a hazardous area. For lower-flashpoint liquids, HSG51 says the whole inside of the cabinet should normally be taken to be zone 2, a place where an explosive atmosphere is not likely in normal operation. Ignition sources must be kept out, so never put ordinary electrical equipment, such as a charger, inside one.
Store larger quantities in a dedicated store. HSG51 says a flammable liquid store should be used only for storage; sampling, dispensing, mixing and repacking belong in a separate area. For higher-flashpoint liquids kept in drums in a workroom, it recommends at least 3 m, and preferably 5 m, from process activities. Packaging and other combustibles stay out of the store.
Keep flammables away from other dangerous substances. HSG51 says flammable liquids should be stored separately from energetic substances, oxidisers and corrosive materials, which increase the fire risk or can damage the container or cabinet. That applies even when those substances are flammable themselves.
Our guide to the fire triangle explains why separating fuel, oxygen and heat works.
How much flammable liquid can you keep in a workroom?
HSE’s recommended maximum, in HSG51, is 50 litres in cabinets and bins for extremely flammable and highly flammable liquids, and for flammable liquids with a flashpoint below the maximum temperature of the workroom. For other flammable liquids, with a higher flashpoint of up to 60°C, the figure is 250 litres.
These are not legal limits. HSG51 calls them “recommended maxima representing industry safe practice, rather than absolute limits”. If you need more, say in a large open-plan workshop, record your justification in the risk assessment, treating mixed storage as if everything had the lowest flashpoint present. And 50 litres is a ceiling, not a target: DSEAR’s first control measure is to reduce the quantity of dangerous substances to a minimum.
Under the GB CLP Regulation, extremely and highly flammable liquids (Categories 1 and 2) have a flashpoint below 23°C, and Category 3 flammable liquids have a flashpoint between 23°C and 60°C. The signal word and hazard statement on the label, together with section 9 of the safety data sheet, tell you which applies.
Can you decant chemicals into another container?
Only into a suitable container that is labelled before it is used. SR24 says to “never decant concentrate into an unlabelled container” and never store chemicals in open containers. HSE’s Safe Handling of Chemicals poster says to keep chemicals in their original containers, and never in unmarked containers or ones designed for other uses, such as food and drink containers.
A drinks bottle is the worst choice: it invites someone to drink from it, and then nobody knows what they swallowed. The law points the same way. COSHH and DSEAR require the contents and hazards of containers to be clearly identifiable, and the Safety Signs Regulations require hazard pictograms on containers used at work. The exception, for containers used only briefly, applies only where training or other measures give the same protection.
When you do decant, use a container made for the purpose, label it with the product name and hazards, and recap it straight away. Do it in a ventilated area, not inside the store.
Do chemical stores need bunding?
Liquids need secondary containment: a bund, sump, drip tray or spill pallet that catches a leak before it spreads. For chemicals stored in buildings, HSG71 recommends bunded areas, in-rack bunds or drip trays under each pallet. It sets the bunded volume at “110% of the single largest receptacle in the bund”, and says spills must not be able to run into an area where incompatible materials are kept.
Oil has its own law. In England, the Control of Pollution (Oil Storage) (England) Regulations 2001 apply to containers holding more than 200 litres of oil, including petrol, diesel, kerosene, vegetable oils and synthetic lubricating oils. They do not apply to containers inside a building. Secondary containment must hold at least 110% of the container’s capacity. Where it serves several containers, it must hold 110% of the largest or 25% of the total, whichever is greater. A drip tray used for drums must hold at least a quarter of the drums’ combined capacity. GOV.UK’s oil storage guidance gives examples. Wales has its own 2016 regulations, and Scotland and Northern Ireland have separate rules. For oil on building sites, see our guide to environmental awareness in construction.
Bunds only work if they are kept empty. Rainwater, leaked product or rubbish reduces capacity, and HSG71 says rainwater should be removed to maintain it.
What should be in a chemical spill kit?
Whatever the safety data sheets for your stock say. Section 6, “Accidental release measures”, covers precautions and the methods and materials for containment and cleaning up. SR24 says to keep a spill kit nearby and ask your supplier for advice. A kit usually holds absorbent pads, socks or granules, disposal bags, gloves and eye protection, and the absorbents must suit the substances stored.
A spill kit only helps if:
- It is close to the store and unobstructed.
- It is complete, restocked after every use.
- People have practised with it. SR24 says to deal with spills immediately and “practise how to do this”, and COSHH regulation 13 requires arrangements for accidents, incidents and emergencies.
Protect drains first, and put used absorbents in a labelled, lidded bin as hazardous waste.
How do you dispose of out-of-date or unwanted chemicals?
As hazardous waste, through an authorised route, never down a drain or in general waste. GOV.UK lists chemicals, solvents and oils as examples. In England, a business that produces or stores hazardous waste must classify it, separate and store it safely, use registered waste carriers and permitted sites, complete consignment notes, and keep records for three years. The main law behind these hazardous waste rules is the Hazardous Waste (England and Wales) Regulations 2005; Wales, Scotland and Northern Ireland have their own rules.
The easiest waste to manage is the waste you never create. SR24 says to minimise the range of chemicals stored. HSG51 says stores need procedures for stock rotation and inspection based on maximum storage times, and HSG71 advises asking suppliers how long products keep. A product nobody has used in a year is a candidate for disposal, not another year on the shelf.
What training do staff need for chemical storage?
COSHH regulation 12 and DSEAR regulation 9 both require suitable and sufficient information, instruction and training. That includes the substances’ names and risks, access to safety data sheets, the significant findings of the risk assessment and the precautions to take. For a chemical store, people need to know why products are kept where they are, how to decant and label, and what to do about a leak. A storage plan only the manager understands will not survive the first busy week.
Storage decisions belong inside a proper assessment; see our step-by-step COSHH risk assessment guide.
Nexis CPD’s COSHH Awareness course covers the COSHH Regulations, identifying hazardous substances from labels and safety data sheets, and COSHH assessments and controls. It pairs naturally with Respiratory Protective Equipment (RPE), which covers selecting, fitting and maintaining respirators, FFP ratings and face-fit testing — the protection you need when a spill or decanting job releases vapour or dust. The third course is Environmental Awareness at Work, which covers pollution, waste and the legal duty of care for waste.
£9 per course. CPD accredited, 100% online, verifiable e-certificate. Pay for 2, get 3 — any 3 courses for £18. These are CPD-accredited awareness courses, not Ofqual-regulated qualifications. They do not make anyone a COSHH or DSEAR assessor, and they do not replace the employer’s own risk assessments or site-specific training on the store, its equipment and its emergency procedures.
What should a monthly chemical store inspection check?
HSE guidance does not set one frequency for every store. HSG51 says your procedures should set it, and inspections should check for leaks and for damage to containers, packaging and racking. Monthly is a sensible starting point for a small store. Record what you find:
- Stock list matches what is on the shelves, and every product has a current safety data sheet and is covered by a COSHH assessment.
- Quantities are no more than needed, and flammables cabinets are within the recommended maximum.
- Every container is labelled, with labels legible and facing forwards. There are no unlabelled decanted containers and no food or drink containers.
- Caps and lids are closed, and nothing is leaking, bulging, corroded or damaged.
- Segregation is intact: acids away from bleach and alkalis, oxidisers away from flammables, and corrosives out of the flammables cabinet.
- Heavy containers and corrosives are on low shelves, nothing is stacked unstably, and shelving is undamaged.
- Bunds, sumps and drip trays are clean, dry, undamaged and free of rainwater, rubbish and leaked product.
- Flammables cabinet doors close properly, and there are no ignition sources, heaters or chargers nearby.
- No combustible rubbish is in the store, and ventilation openings are clear.
- Escape routes and the store door are clear, and the warning sign is in place.
- The spill kit is complete and accessible, and PPE and eye-wash supplies are stocked and in date.
- The store is locked when unattended.
- Out-of-date or unwanted chemicals are identified and booked for hazardous waste collection.
- Defects are recorded, with an owner and a date for each action.
Frequently asked questions
Can bleach and descaler be stored next to each other?
No. Most descalers are acidic, and UKHSA says bleach mixed with acidic products produces chlorine gas. A leak could bring them together, so store bleach away from acids, ideally on a separate unit with its own drip tray.
How much flammable liquid can you keep in a workroom?
HSE’s HSG51 recommends no more than 50 litres in cabinets and bins for extremely and highly flammable liquids, and for flammable liquids with a flashpoint below the workroom’s maximum temperature. The figure is 250 litres for other flammable liquids with a flashpoint up to 60°C. These are recommended maxima, not legal limits.
Do chemicals have to stay in their original containers?
Wherever possible, yes. HSE advises keeping chemicals in their original containers. If you must decant, use a suitable container labelled with the product and its hazards. Never use a drinks bottle or food container, and never leave a decanted chemical unlabelled.
Does oil storage need a bund?
In England, outdoor oil containers over 200 litres at a business must have secondary containment. A bund must hold 110% of a single container, and a drip tray for drums must hold a quarter of the drums’ capacity. Wales, Scotland and Northern Ireland have their own rules.
Where do I find storage instructions for a chemical?
In section 7 of its safety data sheet, “Handling and storage”. Subsection 7.2 covers conditions for safe storage, including incompatibilities, ventilation and quantity limits. Section 10 lists materials the product reacts with. HSE says that by law, the supplier of a product that is dangerous for supply must provide one.
Who should have access to a chemical store?
Only authorised people who have been trained, according to HSE’s COSHH essentials sheet SR24. Keep it locked when unattended and make sure every user knows the segregation rules and the spill procedure.
This article is general information, not legal advice — always follow the product’s safety data sheet. It summarises HSE guidance and the law in Great Britain as at 15 October 2026; oil storage and hazardous waste rules differ between England, Wales and Scotland. Always follow your employer’s COSHH and DSEAR risk assessments. Nexis CPD courses are CPD-accredited awareness training, not regulated qualifications.