9 Classes of Hazardous Materials - UN Classification
The United Nations & regulatory bodies like US Department of Transportations (DOT) divide hazardous materials (hazmat) into 9 distinct hazard classes based on the specific risks they pose during transport and storage. Here are more details to update health & safety knowledge who is engaged in transport/storage and handling of hazardous chemicals.
Ganpat Shinde
11/9/20264 min read
Introduction
Hazardous materials are substances or articles that can pose risks to human health, safety, property and the environment during transportation, storage, handling and use. These materials may cause fire, explosion, poisoning, chemical burns, radiation exposure or environmental pollution if not handled properly.
To ensure safe transportation and handling worldwide, the United Nations (UN) has established a classification system that divides dangerous goods into 9 major classes, based on their physical, chemical and hazardous properties.
Understanding these nine classes helps workers, transporters, warehouse personnel and safety professionals identify hazards and take appropriate precautions.
The 9 Classes of Hazardous Materials
Class 1 – Explosives
Materials that can cause explosions due to heat, shock, friction or fire.
Examples: Fireworks, ammunition, blasting explosives and detonators.
Safety precautions: Keep away from heat, flames, sparks and impact. Follow approved storage and handling procedures.
Class 2 – Gases
Gases transported under pressure, liquefied or refrigerated.
2.1: Flammable gases – LPG, hydrogen, propane.
2.2: Non-flammable, non-toxic gases – nitrogen, oxygen, carbon dioxide.
2.3: Toxic gases – chlorine, ammonia (anhydrous).
Safety precautions: Secure cylinders upright, protect valves, provide ventilation and keep flammable gases away from ignition sources.
Class 3 – Flammable Liquids
Liquids that produce vapours capable of catching fire.
Examples: Petrol, diesel, ethanol, paints and solvents (depending on their properties).
Safety precautions: Avoid ignition sources, ensure proper ventilation, control static electricity and use approved containers.
Class 4 – Flammable Solids
Materials that can catch fire easily, ignite spontaneously or release flammable gases when in contact with water.
4.1: Flammable solids – matches, certain combustible powders.
4.2: Substances liable to spontaneous combustion – certain oily waste and self-heating materials.
4.3: Dangerous when wet – calcium carbide, sodium.
Safety precautions: Prevent friction, heat and sparks. Keep water-reactive substances dry and segregated.
Class 5 – Oxidizing Substances and Organic Peroxides
Materials that can cause or intensify fire by releasing oxygen or supporting combustion.
5.1: Oxidizing substances – hydrogen peroxide, ammonium nitrate.
5.2: Organic peroxides – certain peroxide-based chemical products.
Safety precautions: Keep away from combustible materials, oils and incompatible chemicals. Follow temperature-control requirements where applicable.
Class 6 – Toxic and Infectious Substances
Materials that can cause poisoning, illness or infection.
6.1: Toxic substances – certain pesticides, cyanide compounds.
6.2: Infectious substances – materials containing disease-causing microorganisms.
Safety precautions: Avoid direct contact and inhalation. Use suitable PPE, sealed packaging and appropriate biological or chemical handling procedures.
Class 7 – Radioactive Materials
Materials that emit ionizing radiation, which can harm living tissues.
Examples: Radioactive isotopes, uranium compounds and radioactive sources used in industrial radiography and medical applications.
Safety precautions: Follow ALARA principles – Time, Distance and Shielding. Use approved containers, radiation monitoring and authorized handling procedures.
Class 8 – Corrosive Substances
Chemicals that can destroy living tissues or corrode metals.
Examples: Sulphuric acid, hydrochloric acid, nitric acid and sodium hydroxide.
Safety precautions: Wear chemical-resistant gloves, goggles, face shields and protective clothing. Provide suitable spill-control arrangements and emergency washing facilities.
Class 9 – Miscellaneous Dangerous Substances and Articles
Materials that present transportation hazards but do not fall under the other eight classes.
Examples: Lithium batteries, environmentally hazardous substances and certain elevated-temperature substances.
Safety precautions: Follow specific packaging, labelling, segregation and transportation requirements for the material.
General Safety Requirements for Hazardous Materials
Regardless of the classification, workers should follow these important safety practices:
Identify the hazardous material before handling it.
Read the Safety Data Sheet (SDS) carefully.
Check UN identification numbers and hazard labels.
Use appropriate personal protective equipment (PPE).
Store incompatible chemicals separately.
Ensure proper ventilation and fire protection.
Provide spill-control and emergency-response arrangements.
Train workers in safe handling, storage and transportation.
Report leaks, spills and unsafe conditions immediately.
Conclusion
The UN classification system provides a standard method for identifying hazardous materials and communicating their risks. Every worker involved in manufacturing, storage, handling and transportation must understand these nine classes. Proper identification, labelling, segregation, PPE and emergency preparedness can prevent serious accidents and protect human life and the environment.
Remember: Identify the Hazard – Understand the Risk – Follow Safety Precautions.
Know Your Hazardous Materials Before You Handle Them!