Chemical Storage Segregation: GHS Compatibility Rules for Warehouses
Storing incompatible chemicals together is one of the most common causes of warehouse fires, toxic gas releases, and explosions. GHS classification provides the foundation for determining which substances must be segregated.
Why Segregation Matters
When incompatible chemicals mix — through a spill, leak, or fire — the results can be catastrophic:
- Acids + cyanides → releases hydrogen cyanide gas (fatal at low concentrations)
- Oxidisers + flammables → accelerates fire dramatically, may cause explosion
- Water-reactive substances + water → releases flammable or toxic gas
GHS pictograms and H-statements directly indicate incompatibility risks. Understanding the system allows warehouse managers to design safe storage layouts.
The Six Primary Segregation Groups
Group 1: Flammables and Combustibles
GHS indicator: GHS02 pictogram, H224/H225/H226/H228
Store in: Dedicated flammable storage cabinets or rooms with explosion-proof electrical systems.
Segregate from: Oxidisers (Group 2), corrosives (Group 3), compressed gases.
Group 2: Oxidisers
GHS indicator: GHS03 pictogram, H270/H271/H272
Store in: Cool, dry, well-ventilated area. Non-combustible shelving only.
Segregate from: All flammables and combustibles, organic materials, reducing agents.
Group 3: Corrosives (Acids and Bases)
GHS indicator: GHS05 pictogram, H314
Store in: Acid-resistant trays with secondary containment. Separate acids from bases.
Segregate from: Flammables (acids can react), cyanides (acids release HCN), water-reactive materials.
Group 4: Acute Toxics (Cat 1–3)
GHS indicator: GHS06 pictogram, H300/H301/H310/H311/H330/H331
Store in: Locked, well-ventilated cabinets. Access restricted to authorised personnel.
Segregate from: General chemical storage areas. Keep separate from food-related materials.
Group 5: Water-Reactive Substances
GHS indicator: GHS02 with H260/H261
Store in: Completely dry conditions. No sprinkler systems in storage zone (use sand or dry powder systems instead).
Segregate from: Aqueous solutions, acids, humid environments.
Group 6: Compressed Gases
GHS indicator: GHS04 pictogram, H280/H281
Store in: Secured upright with chains, away from heat sources. Separate flammable gases from oxidising gases.
Segregate from: Flammable materials (for oxidising gases), ignition sources (for flammable gases).
Compatibility Matrix Summary
| Flammables | Oxidisers | Acids | Bases | Toxics | Water-Reactive | |
|---|---|---|---|---|---|---|
| Flammables | ✅ | 🔴 | ⚠️ | ✅ | ⚠️ | 🔴 |
| Oxidisers | 🔴 | ⚠️ | ⚠️ | ⚠️ | ⚠️ | 🔴 |
| Acids | ⚠️ | ⚠️ | ✅* | 🔴 | ⚠️ | 🔴 |
| Bases | ✅ | ⚠️ | 🔴 | ✅* | ✅ | ⚠️ |
| Toxics | ⚠️ | ⚠️ | ⚠️ | ✅ | ✅ | ⚠️ |
| Water-Reactive | 🔴 | 🔴 | 🔴 | 🔴 | ⚠️ | ✅* |
🔴 = Strictly prohibited | ⚠️ = Separate with distance/containment | ✅ = Generally compatible | *Within group, further sub-segregation may apply
OSHA and REACH Requirements
OSHA 29 CFR 1910.106 (flammable liquids): Specifies storage cabinet requirements, quantities, and separation distances.
OSHA 29 CFR 1910.1000: Requires hazard communication including storage incompatibility information.
CLP Regulation (EU): Section 7 of the SDS must include information on conditions for safe storage, including incompatibilities.
NFPA 400 (Hazardous Materials Code): Provides detailed segregation distances and storage limits by hazard class.
Practical Implementation Steps
- Audit your inventory — list all chemicals with their GHS classification
- Assign each chemical to a segregation group — use GHS02–GHS09 pictograms as primary indicators
- Map your storage areas — designate zones for each group
- Install secondary containment — drip trays sized for the largest container
- Label storage zones — use GHS-compliant signage
- Train personnel — ensure all staff understand segregation rules
- Review after every new chemical addition — compatibility check before storage
Using the Storage Compatibility Tool
Our Chemical Storage Compatibility Matrix lets you input a list of chemicals and instantly generates a colour-coded compatibility grid — showing which combinations are prohibited, conditional, or safe.
Related Resources
- GHS H-Statements Complete Guide — understand H-codes that indicate storage hazards
- GHS Signal Words: Danger vs Warning — severity levels for storage classification
- How to Calculate ATE for Chemical Mixtures — toxicity data needed for storage decisions
- Storage Compatibility Matrix →
Reference: UN GHS Rev.9. OSHA 29 CFR 1910.106 and 1910.1000. CLP Regulation (EC) No 1272/2008, Annex II. NFPA 400:2022.