Safe Storage of Hazardous Substances

Safe storage of hazardous substances is a legal requirement under COSHH and DSEAR regulations. Proper storage prevents fires, explosions, chemical reactions, environmental contamination, and worker exposure. This guide explains storage requirements, segregation rules, and practical arrangements to keep hazardous substances secure and compliant.

Why safe storage matters

Improper storage of hazardous substances can result in:

Health risks:

• Vapor release from poorly sealed containers causing exposure
• Skin contact from leaking or damaged containers
• Poisoning from unlabeled or improperly stored substances
• Asphyxiation from oxygen-displacing gases in confined spaces

Safety risks:

• Fires from flammable substances near ignition sources
• Explosions from vapor accumulation in poorly ventilated areas
• Chemical reactions from incompatible substances stored together
• Structural damage from corrosive substance leaks

Environmental risks:

• Ground contamination from spills and leaks
• Water pollution from inadequate containment
• Air pollution from vapor release

Legal risks:

• HSE enforcement action (improvement/prohibition notices)
• Prosecution and fines for breaches of COSHH and DSEAR
• Environmental enforcement by the Environment Agency
• Increased insurance premiums or policy voidance

Basic storage requirements

All hazardous substances must be stored in accordance with their Safety Data Sheet (Section 7: Handling and Storage) and with these fundamental principles:

1. Secure and controlled access

Storage areas must be:

• Lockable or otherwise secured against unauthorized access
• Clearly identified with appropriate warning signs
• Accessible only to trained, authorized personnel
• Kept locked when not in active use
• Protected from unauthorized removal or tampering

Why this matters: Prevents untrained staff, contractors, visitors, or intruders from accessing hazardous substances. Reduces risk of theft, misuse, or accidental exposure.

2. Suitable containers

Substances must be kept in:

• Original containers whenever possible (designed for the substance)
• Compatible containers if decanting is necessary (check SDS for material compatibility)
• Properly sealed containers to prevent evaporation or spillage
• Undamaged containers (no cracks, corrosion, or leaks)
• Appropriately sized containers (don't overfill or leave excessive headspace)

3. Clear labeling

Every container must be labeled with:

• Substance name (trade name and/or chemical name)
• Hazard pictograms (as per the original label)
• Signal word (Danger or Warning)
• Key hazard statements (H-statements)
• Precautionary statements (P-statements)
• Supplier information

If you decant into secondary containers, you must recreate this labeling. Never remove or obscure original labels.

4. Appropriate storage location

Choose storage locations that:

• Are away from main work areas where possible
• Have adequate ventilation (natural or mechanical)
• Are protected from extreme temperatures (unless substance requires refrigeration)
• Are away from ignition sources (for flammables)
• Are protected from direct sunlight (which can degrade some substances or increase vapor pressure)
• Are on suitable surfaces (impermeable, resistant to the substances stored)
• Have spill containment (bunds, drip trays, or sealed flooring)

Segregation of incompatible substances

Some substances react dangerously when they come into contact. Segregation prevents:

• Fires and explosions (e.g., flammables near oxidizers)
• Toxic gas release (e.g., acids and cyanides)
• Violent reactions (e.g., acids and alkalis)
• Accelerated decomposition (e.g., some substances become unstable when contaminated)

Common incompatibilities:

Segregation methods:

Physical separation:

• Minimum 3 meters distance between incompatible classes
• Physical barriers (walls, partitions, separate rooms)
• Different buildings for very large quantities
• Different cabinets within the same room

Spill containment separation:

• Ensure incompatibles cannot mix even if both containers leak
• Use drip trays and bunds that isolate different substance classes
• Never rely on a common bund for incompatible substances

Vertical separation:

• Store heavy containers on lower shelves (less likely to fall)
• Store corrosives on lower shelves (won't drip onto other substances if they leak)
• Never store liquids above powders or reactive substances

Specific storage requirements by hazard class

Different hazard classes have specific storage needs:

Flammable and highly flammable substances

Requirements:

• Dedicated flammable storage cabinet (metal, designed for the purpose)
• Away from ignition sources (at least 3 meters from heaters, electrical equipment, naked flames)
• Adequate ventilation to prevent vapor accumulation (preferably vented cabinet or ventilated room)
• Explosion-proof electrical fittings in areas where flammable vapors may accumulate (required under DSEAR)
• Fire-resistant construction for storage rooms (30-60 minute fire rating)
• Maximum quantities limited in work areas (only amount needed for current work)

DSEAR considerations: If you store more than 50 liters of flammable liquid or equivalent, DSEAR likely applies. You must:

• Assess fire and explosion risks
• Classify areas where explosive atmospheres may occur (Zone 0, 1, or 2)
• Ensure electrical equipment is suitable for the zone
• Eliminate or control ignition sources
• Provide explosion relief or suppression if needed

Oxidizing substances

Oxidizers intensify fires and can cause normally non-flammable materials to burn fiercely.

Requirements:

• Separate from flammables and combustibles (different cabinet or room)
• Separate from reducing agents (metals, organic materials, acids)
• Cool, dry storage (heat can cause decomposition)
• Non-combustible shelving and containers
• Away from sources of heat or friction
• Clearly identified storage with "OXIDIZING AGENT" warning

Common oxidizers: hydrogen peroxide, chlorine, nitric acid, potassium permanganate, calcium hypochlorite.

Corrosive substances (acids and alkalis)

Corrosives can cause severe burns to skin and eyes and corrode storage containers and structures.

Requirements:

• Acids and alkalis stored separately (violent reaction if mixed)
• Bunded storage to contain leaks and spills
• Corrosion-resistant shelving (plastic-coated or stainless steel)
• At or below eye level (reduces splash risk when retrieving)
• Away from metals they could corrode
• Secondary containment (store bottles in plastic trays or bins)
• Ventilated storage to remove corrosive vapors

Toxic and very toxic substances

Requirements:

• Locked storage (not just closed—actively locked with key control)
• Access restricted to specific authorized persons
• Inventory control (log of what's held, who removed it, when, how much)
• Separate from food storage and preparation areas (different room or building)
• Appropriate spill containment
• Specialist disposal arrangements for waste

Compressed gases

Cylinders of compressed or liquefied gases have unique storage needs:

Requirements:

• Secured upright (chained or strapped to prevent falling)
• Protected from mechanical damage (away from impact, protected from vehicles)
• Protected from heat (away from radiators, direct sunlight)
• Separate full and empty cylinders (clearly labeled)
• Valve protection caps fitted when not connected
• Well-ventilated area (especially for toxic or asphyxiant gases)
• Separate flammable gases from oxygen (at least 3 meters)
• Warning signs identifying gas type and hazards

Never store cylinders in confined spaces, basements, or areas where leaking gas could accumulate.

Substances hazardous to the aquatic environment

These require storage that prevents environmental contamination:

Requirements:

• Bunded storage (bund capacity at least 110% of largest container)
• Impermeable floor and drainage that doesn't connect to surface water drains
• Located away from drains, water courses, and groundwater
• Spill kits readily available
• Regular inspection for leaks or container damage
• Emergency arrangements to prevent contaminated water reaching drains

Storage capacity and quantities

The amount of hazardous substance you store affects the risk and regulatory requirements:

Minimize quantities held:

• Only store what you need — Order smaller quantities more frequently
• Remove out-of-date materials — Don't hoard substances "just in case"
• Use oldest stock first — Rotate stock to prevent deterioration
• Dispose of surplus — Arrange professional disposal rather than indefinite storage
• Centralize storage — Don't have multiple small storage points; consolidate where possible

Segregate storage from use:

• Main storage — Bulk or reserve quantities in dedicated storage area
• Work area storage — Only the amount needed for current tasks (typically one day's supply)
• Return unused portions to main storage at end of shift
• Don't leave substances out overnight or when not in use

Ventilation requirements

Adequate ventilation in storage areas prevents vapor accumulation and reduces exposure if containers leak.

Natural ventilation:

Suitable for:

• Small quantities of low-volatility substances
• Non-flammable, non-toxic substances
• Storage areas used infrequently

Requirements:

• Permanent ventilation openings (high and low level for cross-ventilation)
• Minimum airflow to prevent stagnant air
• Openings protected from weather (vents, louvers)

Mechanical ventilation:

Required for:

• Large quantities of flammable or toxic substances
• Highly volatile substances
• Areas where natural ventilation is insufficient
• Enclosed rooms without windows

Requirements:

• Extract ventilation at rate sufficient to prevent vapor buildup
• Extract positioned at low level for heavier-than-air vapors (e.g., many solvents)
• Extract positioned at high level for lighter-than-air vapors (e.g., ammonia, methane)
• Discharged safely away from windows, doors, air intakes
• Regularly maintained and tested

Bunding and spill containment

Bunds and secondary containment prevent spills from spreading and contaminating the environment.

When bunding is required:

• Liquids that are toxic, corrosive, or environmentally hazardous
• Large quantities (typically >200 liters, but assess based on risk)
• Storage near drains, water courses, or groundwater
• As specified in the SDS (Section 7)
• To comply with environmental permits or pollution prevention guidelines

Bund design requirements:

Capacity:

• At least 110% of the largest container in the bund, or
• 25% of total capacity of all containers, whichever is greater
• Sufficient freeboard to accommodate rainwater (for outdoor bunds)

Construction:

• Impermeable — Resistant to the substances stored
• Liquid-tight — No gaps, cracks, or drainage points
• Structurally sound — Can withstand weight and chemical attack
• No drainage unless to a sealed containment system

Access:

• Easy access for container placement and removal
• Ramps or steps if needed for safe manual handling
• No compromise to bund integrity

Secondary containment alternatives:

• Drip trays under smaller containers (must hold full contents of container)
• Plastic bins or tubs holding multiple smaller containers
• Double-walled containers for high-risk substances
• Sealed rooms with impermeable floors and raised thresholds (for indoor storage)

Temperature control and environmental conditions

Many substances have specific storage temperature requirements:

Temperature-sensitive substances:

Refrigerated storage (2-8°C):

• Some biological agents, vaccines, culture media
• Certain reactive chemicals that decompose at room temperature
• Must use dedicated chemical refrigerator (not the staff kitchen fridge!)

Frozen storage (below 0°C or lower):

• Some laboratory reagents and biological samples
• Certain reactive or unstable chemicals

Room temperature (15-25°C):

• Most common chemicals
• Avoid temperature extremes and fluctuations

Keep cool (below 25°C):

• Many flammables (reduces vapor pressure and risk)
• Some substances that decompose or react at higher temperatures

Humidity control:

• Water-reactive substances must be kept dry (use sealed containers, desiccants)
• Hygroscopic substances (absorb moisture from air) need moisture-proof containers
• Corrosion-prone containers (metal drums) should be stored in low-humidity areas

Light protection:

Some substances degrade when exposed to light:

• Store in opaque containers or amber glass if light-sensitive
• Keep away from direct sunlight
• Use tinted windows or blinds in storage rooms if necessary

Check Section 7 of the SDS for specific storage conditions.

Emergency arrangements for storage areas

Storage areas must have emergency equipment and procedures:

Essential emergency equipment:

Spill control:

• Spill kits appropriate to substances stored (absorbent granules, pads, booms, neutralizers)
• Cleanup tools (shovels, brushes, disposal bags)
• PPE for spillage response (gloves, goggles, apron or coveralls)
• Warning signs ("Wet Floor," "Spill in Progress")

Fire fighting:

• Fire extinguishers suitable for substances stored:
  • CO₂ or dry powder for flammable liquids
  • Water or foam for general combustibles
  • NOT water on water-reactive substances or electrical fires
• Fire blanket for small fires or personnel on fire
• Clearly marked with substance compatibility

First aid and decontamination:

• Eyewash station if corrosives stored (plumbed or self-contained)
• Safety shower if large quantities of corrosives or large splash risk
• First aid kit with appropriate treatments (burn dressings, eye pads)
• Emergency contact numbers displayed

Emergency procedures:

Spill response:

1. Alert others and evacuate if necessary
2. Eliminate ignition sources (for flammables)
3. Wear appropriate PPE
4. Contain the spill (absorbents, booms, close bund valves)
5. Neutralize if appropriate (acids/alkalis)
6. Collect waste for disposal
7. Ventilate area
8. Report incident and review controls

Fire response:

1. Raise alarm
2. Evacuate
3. Call fire brigade
4. Tackle fire only if safe (small fire, correct extinguisher, trained, escape route clear)
5. Inform fire brigade of substances involved (provide SDS if possible)

Exposure response:

1. Remove person from exposure
2. Follow first aid measures in Section 4 of SDS
3. Seek medical attention (take SDS to A&E)
4. Report under RIDDOR if required

Maintaining storage areas

Regular maintenance prevents deterioration of storage areas and containers:

Daily checks:

• Visual inspection for leaks, spills, or damaged containers
• Check doors and locks functioning
• Ensure area is tidy and clear of obstructions
• Verify emergency equipment accessible

Weekly checks:

• More thorough inspection of containers and storage equipment
• Check ventilation operating (mechanical systems)
• Housekeeping (clean up any dust, empty drip trays if dry)
• Check temperature if controlled storage

Monthly checks:

• Inspect all containers systematically for damage, corrosion, label legibility
• Test emergency equipment (eyewash, safety shower, fire extinguishers—visual check/pressure gauge)
• Review inventory and remove out-of-date materials
• Check bunding and secondary containment for integrity

Annual checks:

• Full review of storage risk assessment
• Review emergency procedures and conduct drills
• Service mechanical ventilation
• Service fire extinguishers (by competent person)
• Audit compliance with storage requirements

Storage of waste hazardous substances

Waste substances can be as hazardous as new materials:

Requirements:

• Separate storage for waste (not mixed with usable stock)
• Clearly labeled as waste, with contents identified
• Same segregation rules apply (don't mix incompatible wastes)
• Secure to prevent unauthorized disposal or environmental release
• Collected and disposed by licensed waste carrier
• Waste transfer notes kept for 2 years (3 years in Scotland)
• Hazardous waste consignment notes kept for 3 years (if classified as hazardous waste)

Never:

• Pour waste down drains (unless specifically permitted under trade effluent consent)
• Mix different waste streams (makes disposal more difficult and expensive)
• Store waste indefinitely (arrange regular collections)
• Dispose of as general waste (illegal and dangerous)

Frequently asked questions

Next steps

To complete COSHH assessments covering storage:

What is a COSHH Assessment? →

Understand legal requirements for COSHH assessments:

COSHH Assessment Requirements →

Learn about exposure limits that might apply during storage incidents:

Workplace Exposure Limits (WELs) →

Check your COSHH obligations:

COSHH Checker Tool →

Related articles:

• What is a COSHH Assessment?
• What is COSHH?
• Workplace Exposure Limits

Useful tools:

• COSHH Checker
• Risk Assessment Tool