HSG51 is HSE guidance for the safe storage of flammable liquids in workplace containers up to 1,000 litres capacity. It covers fire and explosion risks, storage location, separation, ventilation, spill containment, ignition control and emergency arrangements. HSG51 supports compliance with DSEAR but is not itself legislation, and the appropriate controls should be determined through the workplace risk assessment.
HSG51, The storage of flammable liquids in containers, is guidance published by the Health and Safety Executive for people responsible for safely storing flammable liquids at work.
The current publication is the third edition, published in 2015.
It applies to flammable liquids stored in containers with a capacity of up to 1,000 litres.
The guidance explains the fire and explosion hazards associated with flammable liquids and describes practical measures that can be used to control those risks.
HSG51 complements the requirements of the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) and should be considered alongside the site’s DSEAR risk assessment.
No. HSG51 is HSE guidance rather than a separate piece of legislation.
The principal legal duties relating to workplace fire and explosion risks from dangerous substances are contained in DSEAR.
HSG51 provides practical guidance on how those risks can be controlled when flammable liquids are stored in containers.
Alternative arrangements may be appropriate where they provide an equivalent level of safety and can be justified through the risk assessment.
See our DSEAR Regulations 2002 guide for further information on the underlying legal duties.
For the purposes of HSG51, a flammable liquid is generally a liquid with a flashpoint of 60°C or below.
The guidance is principally concerned with liquids capable of producing a flammable atmosphere under the conditions in which they are stored.
It can therefore also be relevant to some liquids with a flashpoint above 60°C where workplace or environmental conditions mean that they may foreseeably be stored at or above their flashpoint.
The level of control required should reflect the actual fire and explosion risk rather than relying solely on the nominal flashpoint classification.
Yes. HSG51 does not cover certain flammable liquids presenting special hazards that require more specific precautions.
The guidance gives examples including:
Where substances have unusual reactive or unstable properties, specialist guidance and competent advice may be required.
Where flammable liquids are intentionally present at a workplace, DSEAR requires the employer to assess the risks they may create.
For storage activities, relevant factors can include:
The controls selected should be proportionate to the hazards and actual storage arrangements at the site.
Where practicable, outdoor storage can provide significant safety advantages because leaked vapours can disperse more readily.
HSG51 describes an unenclosed and uncongested outdoor location at ground level as the ideal situation for preventing dangerous accumulations of flammable vapour.
Outdoor storage must still be suitably designed and managed. Important considerations include:
HSG51 provides recommended minimum separation distances between outdoor flammable-liquid storage and occupied buildings, site boundaries, process units, flammable-liquid storage tanks or ignition sources.
| Quantity stored | Recommended minimum separation distance |
|---|---|
| Up to 1,000 litres | 2 metres |
| 1,000 to 100,000 litres | 4 metres |
| Above 100,000 litres | 7.5 metres |
These are HSG51 guidance values based on accepted industry practice rather than universal statutory distances.
A site’s risk assessment may identify circumstances where greater separation is appropriate, for example because of nearby vulnerable populations, process plant, limited emergency-service access or other site-specific hazards.
Where the recommended distance cannot be achieved, HSG51 describes circumstances in which suitable fire-resisting barriers and other protective measures may be considered.
Potentially. HSG51 recognises that where the recommended separation distance cannot be achieved, a suitable physical barrier of fire-resisting construction may form part of an alternative arrangement.
The design of the fire wall must still provide effective protection and should not interfere with other safety requirements such as ventilation and escape.
HSG51 recommends that a fire wall used for this purpose is at least as high as the container stack and has a minimum height of 2 metres.
The suitability of any reduced-distance arrangement should be established through the site-specific risk assessment.
HSG51 recommends that flammable-liquid storage areas have adequate means to prevent uncontrolled spills or leaks spreading beyond the storage area.
For metal containers, HSG51 describes containment capable of holding at least 110% of the capacity of the largest container as a typical arrangement.
Containment can be provided by measures such as:
The containment arrangements must also take account of the type of containers involved. Plastic containers can fail rapidly when exposed to fire, potentially releasing a much greater proportion of the stored inventory.
The 110% figure should therefore not be treated as a universal rule that automatically determines the correct containment capacity for every flammable-liquid installation.
Flammable-liquid storage should be arranged to prevent dangerous accumulations of vapour arising from foreseeable leaks or releases.
Where storage takes place indoors, adequate ventilation is therefore important.
For dedicated storage buildings using natural ventilation, HSG51 describes fixed openings at high and low level, preferably on opposite walls to encourage cross-flow ventilation.
Where suitable cross-flow can be achieved, the guidance recommends a total free ventilation area equivalent to at least 1% of the total area of the walls and roof of the store.
A larger free area may be necessary where the building is obstructed or sheltered or where the ventilation openings cannot be arranged to provide effective cross-flow.
Mechanical exhaust ventilation may be needed where adequate natural ventilation cannot be achieved.
Many flammable-liquid vapours are heavier than air and can accumulate close to floor level, particularly in pits, drains, channels and other low areas.
HSG51 therefore recommends that ventilation arrangements provide suitable air movement at both high and low levels.
Storage design should also consider whether vapours could migrate into drains, pits or other enclosed spaces where an explosive atmosphere could develop.
Where flammable liquids are stored at or above their flashpoint, or where this could reasonably occur, DSEAR requires the potential extent of any explosive atmosphere to be assessed.
This process is known as hazardous-area classification.
The assessment determines where explosive atmospheres may occur and which hazardous zones are appropriate.
HSG51 provides guidance for common storage arrangements, but the final classification must reflect the actual substances, ventilation and release scenarios at the workplace.
Once potential flammable atmospheres have been identified, sources capable of igniting those atmospheres must be controlled.
HSG51 identifies potential ignition sources including:
Equipment used within a classified hazardous area should be suitable for the zone and explosive atmosphere identified through the DSEAR assessment.
No. HSG51 advises that flammable liquids should be stored separately from incompatible dangerous substances.
This can include substances that could increase the likelihood or severity of a fire or compromise the integrity of flammable-liquid containers.
Examples can include:
Combustible materials such as cardboard and unnecessary packaging should also not be allowed to accumulate within a flammable-liquid store.
HSE’s HSG71 chemical warehousing guidance provides further information on chemical segregation.
Where limited quantities of flammable liquids are required for current work, HSG51 allows for suitable closed containers to be stored in appropriately designed fire-resisting cabinets or bins.
These should be positioned in a suitable, well-ventilated location and should not compromise escape routes.
HSG51 recommends keeping the quantity in the work area to the minimum needed for the activities being carried out.
For cabinets and bins used in process areas, workrooms, laboratories and similar locations, HSG51 gives recommended maximum quantities of:
These figures are recommended maxima representing good industry practice, not absolute legal limits.
Where a workplace proposes to exceed them, HSG51 advises that the justification should be considered and recorded through the risk assessment, taking account of matters such as room size, occupancy, quantities handled, ventilation, ignition sources, fire resistance and means of escape.
HSG51 recommends that cabinets and bins used for limited quantities of flammable liquids in workrooms are capable of retaining spills.
The guidance specifies a containment capacity of 110% of the volume of the largest vessel normally stored within the cabinet or bin.
The cabinet should also be positioned so that it does not jeopardise escape and should be separated from incompatible substances.
Not necessarily. HSG51 describes minimum construction principles for fire-resisting cupboards and bins and also identifies BS EN 14470-1 as a more demanding cabinet performance standard.
HSG51 makes clear that standards going beyond the minimum requirements of UK health and safety legislation are not automatically legal requirements simply because they provide a higher level of performance.
However, an EN 14470-1 cabinet may be selected where the risk assessment, specification or organisation’s safety requirements call for tested cabinet fire performance.
For flammable-liquid storerooms located within buildings used for other purposes, HSG51 recommends that relevant internal partitions provide a minimum of 30 minutes fire resistance for integrity, insulation and, where applicable, load-bearing capacity.
Doors forming part of a fire-resisting barrier should also be appropriately fire resisting and self-closing.
The store must still have suitable ventilation, spill containment and means of escape, and its location should not place occupants elsewhere in the building at unacceptable risk.
HSG51 recommends that a dedicated storage facility is used solely for storage rather than for activities likely to release flammable liquid or vapour.
Activities such as:
should normally be carried out in a separate area designed and controlled for those operations.
HSE’s HSG140 guidance provides more detailed advice on the safe use and handling of flammable liquids.
Flammable-liquid storage should be protected against uncontrolled or unauthorised access.
Depending on the risk, this can include:
Security measures must not compromise ventilation, emergency escape or other safety requirements.
Storage facilities should be maintained so that their safety features remain effective.
HSG51 recommends suitable operational procedures for storage, stock rotation and inspection.
Inspections may need to consider:
The frequency of inspection should reflect the storage conditions, substances involved and risks identified at the site.
Employers should plan for foreseeable leaks, spills, fires and other incidents involving flammable liquids.
Depending on the storage facility, emergency arrangements can include:
People expected to use fire-fighting or emergency equipment should receive appropriate training.
HSE publishes three principal guidance documents covering different aspects of flammable-liquid fire and explosion risk:
The correct guidance therefore depends on whether the activity involves container storage, use and handling, or tank storage.
A workplace may need to consider more than one document where several of these activities take place.
Chemstore provides storage solutions for flammable liquids ranging from indoor safety cabinets to dedicated stores for drums and IBCs.
For larger quantities, the Firevault range provides dedicated fire-rated flammable-liquid storage options for drums, IBCs and walk-in applications.
For smaller indoor quantities, Chemstore supplies flammable-liquid safety cabinets, including options tested to BS EN 14470-1.
The appropriate solution should be selected according to the liquids, quantities, container types, storage location, fire and explosion risks and findings of the DSEAR assessment.
A storage product does not by itself make a workplace compliant with DSEAR or HSG51 guidance.
The Health and Safety Executive provides HSG51 directly on its website.
This page summarises HSE guidance and provides general information only. It does not replace HSG51, DSEAR, other applicable legislation, Safety Data Sheets, a site-specific risk assessment or advice from a competent person.
The storage arrangements required at an individual site should always be determined from the flammable liquids, quantities, containers, workplace conditions, potential release scenarios and fire and explosion risks involved.
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