Key Takeaways
- International regulators sort every hazardous shipment into 9 classes of dangerous goods, from explosives to miscellaneous hazards, based on the UN Model Regulations.
- Each class covers a distinct physical or chemical hazard, and several classes are split further into divisions with their own labeling and packaging rules.
- Packing groups (I, II, III) and subsidiary risks determine how tightly a shipment must be packaged, labeled, and segregated from other cargo.
- Getting classification wrong creates real business risk: rejected bookings, customs delays, fines, and unsafe handling.
- A logistics partner with dangerous goods experience, licensing, and segregated storage like SCGJWD reduces that risk across warehousing and cross-border transport.
Table of Contents
- What Are Dangerous Goods?
- Who Sets the Classification System?
- The 9 Classes of Dangerous Goods Explained
- Packing Groups and Subsidiary Risks
- Choosing a Warehouse or Logistics Partner for Dangerous Goods
- Your Logistics Partner for Dangerous Goods
- Frequently Asked Questions About Classes of Dangerous Goods
A single mislabeled drum of corrosive liquid can stop a container at the port, trigger a customs hold, or put a warehouse crew at risk. For businesses that manufacture, distribute, or export chemicals, batteries, aerosols, or specialty goods, and those that store regulated cargo, understanding the classes of dangerous goods is essential as it determines how cargo gets packaged, documented, stored, and accepted for transport.
So, what are the 9 classes of dangerous goods, and what do they cover? The United Nations Model Regulations divide dangerous goods into nine hazard classes, numbered 1 through 9, based on the primary risk a substance presents during transport: explosion, fire, toxicity, corrosion, radioactivity, or another transport-related hazard. This guide walks through each class, how packing groups and subsidiary risks work, and what businesses should look for in a logistics partner and warehouse service in Thailand that handles regulated cargo.
What Are Dangerous Goods?
Dangerous goods, also called hazardous materials or hazmat, are substances or articles that pose a risk to health, safety, property, or the environment when they move through the supply chain. The risk is not always obvious from the product itself. Lithium batteries inside a consumer electronics shipment, dry ice packed around a biological sample, or a drum of industrial solvent can all be regulated as dangerous goods, depending on their classification, quantity, packaging, and mode of transport.
Businesses encounter dangerous goods across manufacturing, chemicals, pharmaceuticals, electronics, agriculture, and oil and gas. This first step is correct classification, which determines every other requirement, from packaging to labeling, documentation, storage segregation, and the training required of the people who handle it.
Who Sets the Classification System?
The 9 classes of dangerous goods are defined in the United Nations Recommendations on the Transport of Dangerous Goods, often called the "Orange Book." This framework sets the baseline hazard classes and packing group criteria that national and modal regulators build on.
From there, mode-specific bodies apply and adapt the UN framework:
IATA Dangerous Goods Regulations (DGR) govern air transport, working from the International Civil Aviation Organization's (ICAO) Technical Instructions.
The IMDG Code, published by the International Maritime Organization (IMO), governs sea transport.
ADR governs road transport in Europe, and equivalent national regulations, such as the US Department of Transportation's Hazardous Materials Regulations under 49 CFR, apply within individual countries.
The class numbers stay consistent across these frameworks. What changes between modes are the details, including packaging performance standards, quantity limits, documentation, and placarding requirements. A shipper moving the same product by air and by sea needs to confirm both sets of rules.
The 9 Classes of Dangerous Goods Explained
Here is a breakdown of the 9 classes of dangerous goods, what each one covers, and where businesses most commonly encounter them.
Class 1: Explosives
Class 1 covers substances and articles that can explode as a result of a chemical reaction. It splits into six divisions, including
- 1.1 Mass explosion hazard
- 1.2 Projection hazard
- 1.3 Fire hazard, minor blast or projection hazard
- 1.4 No significant hazard
- 1.5 Insensitive substances with mass explosion risk, and
- 1.6 Extremely insensitive articles
Fireworks, ammunition, and blasting agents fall under this class. Class 1 carries some of the strictest handling and transport controls of any hazard class, particularly for air and sea cargo.
Class 2: Gases
Class 2 covers compressed, liquefied, dissolved, or refrigerated gases. It splits into three divisions: 2.1 flammable gases, 2.2 non-flammable and non-toxic gases, and 2.3 toxic gases. Propane, LPG, oxygen cylinders, aerosols, and refrigerant gases are common examples. Gases under pressure pose a physical explosion risk if a cylinder or container fails, adding handling and storage requirements on top of the chemical classification.
Class 3: Flammable Liquids
Under the UN Model Regulations, Class 3 covers liquids and liquid mixtures, generally with a closed-cup flash point of not more than 60 degrees Celsius, subject to specific classification provisions and exceptions. National or mode-specific regulations may use different technical thresholds in certain circumstances. Gasoline, paint thinners, alcohol-based hand sanitizers, and industrial solvents are typical examples.
Class 4: Flammable Solids
Class 4 splits into three divisions: 4.1 flammable solids, self-reactive substances, polymerizing substances, and solid desensitized explosives, 4.2 substances liable to spontaneous combustion, and 4.3 substances that emit flammable gas when wet. Matches, sulfur, sodium, and calcium carbide fall into this class. Division 4.3 in particular needs protection from moisture as much as from ignition sources.
Class 5: Oxidizing Substances and Organic Peroxides
Class 5 is split into 5.1 oxidizing substances and 5.2 organic peroxides. Materials in this class do not necessarily burn on their own, but can accelerate or intensify the combustion of other materials nearby. Ammonium nitrate, hydrogen peroxide, and calcium hypochlorite are common examples, and segregation from flammable and combustible materials in storage is a standard control.
Class 6: Toxic and Infectious Substances
Class 6 splits into 6.1 toxic substances and 6.2 infectious substances. Pesticides and certain industrial chemicals typically fall under 6.1. Division 6.2 carries added regulatory weight for biomedical and healthcare shippers, since it distinguishes Category A infectious substances, capable of causing permanent disability or life-threatening disease, from Category B, which covers infectious substances that do not meet the Category A criteria. Many diagnostic specimens and clinical samples fall into Category B when they meet the applicable criteria; as such, hospitals, laboratories, and diagnostic courier operations need to understand this distinction before they ship.
Class 7: Radioactive Material
Class 7 covers materials with radioactivity levels above defined regulatory thresholds. Packages are grouped into categories: I-White, II-Yellow, and III-Yellow based on radiation levels at the package surface. Medical isotopes, industrial radiography sources, and some gauging instruments fall under this class. Class 7 shipments typically require specialized licensing and handling procedures.
Class 8: Corrosive Substances
Class 8 covers substances that cause visible destruction of, or irreversible damage to, skin on contact, or that corrode metal or transport equipment at a defined rate. Sulfuric acid, sodium hydroxide, hydrochloric acid, and wet-cell lead-acid batteries are common examples. Packaging integrity and compatible container materials matter as much as labeling for this class.
Class 9: Miscellaneous Dangerous Goods
Class 9 covers miscellaneous dangerous substances and articles that present a hazard during transport but do not meet the criteria of Classes 1 through 8, but still presents a transport risk. Lithium-ion and lithium-metal batteries, dry ice, magnetized materials, and environmentally hazardous substances (including marine pollutants) fall under Class 9. This class has become increasingly relevant for e-commerce, electronics, and consumer goods shippers, who often do not realize that products containing lithium batteries, or perishable goods packed with dry ice, are also regulated dangerous goods.
Packing Groups and Subsidiary Risks
Additional factors affect how a shipment gets packaged and documented. Packing groups indicate the degree of danger within a class:
Packing Group I: High danger, requiring the highest level of packaging performance.
Packing Group II: Medium danger.
Packing Group III: Low danger.
The packing group affects the required packaging standard, the applicable quantity limits, and the specific wording used on labels and shipping documents. Not every class uses packing groups; Classes 1, 2, and 7, for example, use their own division and category systems instead.
Subsidiary risks apply when a substance presents more than one hazard. A corrosive liquid that is also toxic, for example, carries Class 8 as its primary hazard and Class 6.1 as a subsidiary risk. Both the primary hazard and subsidiary risk need to appear on the shipping documentation and the package labeling.
Choosing a Warehouse or Logistics Partner for Dangerous Goods
Classification is only the starting point. Businesses that regularly move regulated cargo need a logistics partner that can handle it safely and legally at every stage, from storage through cross-border transport. Consider the following when evaluating a warehouse and logistics partner for dangerous goods:
Licensing and permits. Confirm the provider holds the relevant domestic and international permits for the specific hazard classes your business ships, aside from a general logistics license.
Purpose-built segregation infrastructure. Dangerous goods need physical separation from incompatible materials and from general cargo, based on the segregation rules tied to each class.
Staff certification. Look for documented training and competency records covering the applicable frameworks, such as IATA DGR, IMDG, or ADR, depending on the transport modes involved.
Sector experience. A provider with documented experience in your industry, whether chemicals, pharmaceuticals, electronics, or oil and gas, understands the practical handling issues specific to that cargo.
Digital visibility. Real-time tracking, and temperature logging where relevant, gives businesses visibility into where regulated cargo is and how it has been handled in transit.
Your Logistics Partner for Dangerous Goods
The 9 classes of dangerous goods, as well as their sub-divisions, packing groups, subsidiary risks, give businesses a common reference point across air, sea, road, and rail transport, and informs them of specific requirements of each transport mode and destination. Working with aThailand logistics company that understands dangerous goods classification, from warehousing through cross-border transport, reduces the risk of delays, penalties, and unsafe handling.
SCGJWD Logistics operates as an integrated logistics provider across the ASEAN region, with warehousing and cross-border transport experience that supports businesses moving regulated and specialty cargo. Route and service availability vary by class, cargo type, and destination, so specific requirements should be confirmed directly with the SCGJWD team before booking.
Contact SCGJWD about professional dangerous goods storage and reliable transport for your regulated cargo.
References:
Dangerous Goods Transport Rules & Regulations. Retrieved on 17 September 2026 fromhttps://laws.md.go.th/mrc/detail.php?page=page&id=Dangerous_goods_transport_rules_regulations
Safe Transport of Dangerous Goods by Air. Retrieved on 17 September 2026 fromhttps://www.icao.int/sites/default/files/APAC/Meetings/2020/2020%20COSCAP%20SEAEASA%20DGI/5-Presentations/2-Thailand-Dangerous%20Goods_Cat6_Part%202-Classification.pdf
Dangerous Goods Safety Management. Retrieved on 17 September 2026 fromhttps://www.unescap.org/sites/default/d8files/event-documents/8.2%20Dangerous%20Goods%20Safety%20Management%20In%20Port%20Authority%20of%20Thailand.pdf