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Hazardous materials are any solid, liquid, or gas that can harm people, other living organisms, property, or the environment. They may be radioactive, flammable, explosive, toxic, corrosive, biohazardous, an oxidizer, an asphyxiant, a pathogen, an allergen, or may have other characteristics that render it hazardous in specific circumstances.

Mitigating the risks associated with hazardous materials may require the application of safety precautions during their transport, use, storage and disposal. Most countries regulate hazardous materials by law, and they are subject to several international treaties as well.

Persons who handle dangerous goods will often wear protective equipment, and metropolitan fire departments often have a response team specifically trained to deal with accidents and spills. These teams train with different organizations at a variety of specialized locations. Some of the most well-known in the U.S. and Canada include the California Specialized Training Institute, the Texas A&M TEEX Academy, Signet North America, the Justice Institute of British Columbia, and the U.S. National Fire Academy.

Laws and regulations on the use and handling of hazardous materials may differ depending on the activity and status of the material. For example one set of requirements may apply to their use in the workplace while a different requirements may apply to spill response, sale for consumer use, or transportation. Most countries regulate some aspect of hazardous materials.

The most widely applied regulatory scheme is that for the transportation of dangerous goods. The Committee of Experts on the Transport of Dangerous Goods of the United Nations Economic and Social Council issues Model Regulations on the Transportation of Dangerous Goods. Most regional and national regulatory schemes for hazardous materials are harmonized to a greater or lesser degree with the UN Model Regulation. For instance, the International Civil Aviation Organization has developed regulations for air transport of hazardous materials that are based upon the UN Model but modified to accommodate unique aspects of air transport. Individual airline and governmental requirements are incorporated with this by the International Air Transport Association to produce the widely used IATA Dangerous Goods Regulations. Similarly, the International Maritime Organization has developed the IMO Dangerous Goods Regulations for transportation on the high seas. Many individual nations have also structured their dangerous goods transportation regulations to harmonize with the UN Model in organization as well as in specific requirements.

Dangerous goods are divided into classes on the basis of the specific chemical characteristics producing the risk.

Note: The graphics and text in this article representing the dangerous goods safety marks are derived from the United Nations-based system of identifying dangerous goods. Not all countries use precisely the same graphics (label, placard and/or text information) in their national regulations. Some use graphic symbols, but without English wording or with similar wording in their national language. Refer to the Dangerous Goods Transportation Regulations of the country of interest.

For example, see the Dangerous Goods Safety Marks in the Canadian Transportation of Dangerous Goods Regulations.

The statement above applies equally to all the Dangerous Goods classes discussed in this article.

Classification and labelling summary tables

Class 1: Explosives


Information on this graphic changes depending on which, "Division" of explosive is shipped.

Explosive Dangerous Goods have compatibility group letters assigned to facilitate segregation during transport. The letters used range from A to S excluding the letters I, M, O, P, Q and R. The example above shows an explosive with a compatibility group "A" (shown as 1.1A). The actual letter shown would depend on the specific properties of the substance being transported.

For example, the Canadian Transportation of Dangerous Goods Regulations provides a description of compatibility groups.

  • 1.1 Explosives with a mass explosion hazard
    • Ex: TNT, dynamite, nitroglycerine.
  • 1.2 Explosives with a severe projection hazard.
  • 1.3 Explosives with a fire, blast or projection hazard but not a mass explosion hazard.
  • 1.4 Minor fire or projection hazard (includes ammunition and most consumer fireworks).
  • 1.5 An insensitive substance with a mass explosion hazard (explosion similar to 1.1)
  • 1.6 Extremely insensitive articles.

The United States Department of Transportation (DOT) regulates hazmat transportation within the territory of the US.

1.1 — Explosives with a mass explosion hazard. (nitroglycerin/dynamite)
1.2 — Explosives with a blast/projection hazard.
1.3 — Explosives with a minor blast hazard. (rocket propellant, display fireworks)
1.4 — Explosives with a major fire hazard. (consumer fireworks, ammunition)
1.5 — Blasting agents.
1.6 — Extremely insensitive explosives.

Class 2: Gases

Gases which are compressed, liquefied or dissolved under pressure as detailed below. Some gases have subsidiary risk classes; poisonous or corrosive.
Flammable Gas

  • 2.1 Flammable gas
    • Gases which ignite on contact with an ignition source.

Non Flammable Gas

  • 2.2 Non-Flammable Gases
    • Gases which are neither flammable nor poisonous.

Includes the cryogenic gases/liquids (temperatures of below -100 °C) used for cryopreservation and rocket fuels.
Poison Gas

  • 2.3 Poisonous Gases
    • Gases liable to cause death or serious injury to human health if inhaled.

Class 3: Flammable liquids

Flammable Liquid

Flammable liquids included in Class 3 are included in one of the following packing groups:

  • Packing Group I, if they have an initial boiling point of 35°C or less at an absolute pressure of 101.3 kPa and any flash point;
  • Packing Group II, if they have an initial boiling point greater than 35°C at an absolute pressure of 101.3 kPa and a flash point less than 23°C; or
    • Ex: gasoline (petrol), acetone.
  • Packing Group III, if the criteria for inclusion in Packing Group I or II are not met.
    • Ex: kerosene, diesel.

Note: For further details, check the Dangerous Goods Transportation Regulations of the country of interest.

Class 4: Flammable solids

Flammable Solid

  • 4.1 Flammable solids which are easily ignited and readily combustible.
    • Ex: nitrocellulose, magnesium, safety or strike-anywhere matches.

Spontaneously Combustible

Dangerous when wet

  • 4.3 Substances which emit a flammable gas when wet or react violently with water.

Class 5: Oxidizing Agents & Organic Peroxides


  • 5.1 Oxidizing agents other than organic peroxides.
    • Ex: calcium hypochlorite, ammonium nitrate, hydrogen peroxide, potassium permanganate.

Organic Peroxide

  • 5.2 Organic peroxides, either in liquid or solid form.
    • Ex: benzoyl peroxides, cumene hydroperoxide.

Class 6: Toxic and Infectious Substances


  • 6.1a Toxic substances which are liable to cause death or serious injury to human health if inhaled, swallowed or by skin absorption.
    • Ex: potassium cyanide, mercuric chloride
  • 6.1b (Now PGIII) Toxic substances which are harmful to human health (N.B this symbol is no longer authorized by the United Nations).

Infectious Substance

  • 6.2 Biohazardous substances.

Divided into two categories by the WHO: Cat. A (infectious) and Cat. B (samples).

Class 7: Radioactive Substances


  • Radioactive substances comprise substances or a combination of substances which emit ionizing radiation.
    • Ex: uranium, plutonium.

Class 8: Corrosive Substances

Solids or liquids that can dissolve organic tissue or severely corrode certain metals.

Class 9: Miscellaneous Dangerous Substances

Class Nine

  • Hazardous substances that do not fall into the other categories.
    • Ex: asbestos, air-bag inflators, self inflating life rafts, dry ice.

Other hazardous materials labels (CHIP)

Hazard symbol: harmful Xn, harmful, Xi, Irritant
Hazard symbol: toxic T, toxic
Hazard symbol: corrosive C, corrosive
Hazard symbol: oxidizing O, oxidizing
Hazard symbol: flammable F, flammable
Hazard symbol: explosive E, explosive
Hazard symbol: environmental hazard N, environmental hazard


Uses the standard international UN numbers with a few slightly different signs on the back, front and sides of vehicles carrying hazardous substances. Uses the same "HAZCHEM" as the UK HAZCHEM Code to provide advisory information to emergency services personnel in the event of an emergency situation.


Transportation of dangerous goods (hazardous materials) in Canada by road is normally a provincial jurisdiction. The federal government has jurisdiction over air, most marine, and most rail transport. The federal government acting centrally created the federal transportation of dangerous goods act and regulations, which provinces adoped in whole or in part via provincial transportation of dangerous goods legislation. The result is that all provinces use the federal regulations as their standard within their province; some small variances can exist because of provincial legislation. Creation of the federal regulations was coordinated by Transport Canada. Hazard classifications are based upon the UN Model.

The province of Nova Scotia's dangerous goods transportation act can be viewed at: [1]

The province of Nova Scotia's dangerous goods transportation regulations can can be viewed at: [2]

The federal government's Transport Dangerous Goods website is located at: [3]


The European Union has passed numerous directives and regulations to avoid the dissemination and restrict the usage of hazardous substances, the most famous being the Restriction of Hazardous Substances Directive and the REACH directive. There are also long standing European treaties such as ADR and RID that regulate the transportation of hazardous materials by road, rail, river and inland waterways, following the guide of the UN Model Regulation.

United States


A picture of the U.S. DOT classes in use.

Due to the increased threat of terrorism in the early 21st century, funding for greater HAZMAT-handling capabilities was increased throughout the United States, in recognition of the fact that flammable, poisonous, explosive, or radioactive substances in particular could make attractive weapons for terrorist attacks.

The United States Department of Transportation (DOT) regulates hazmat transportation within the territory of the US. The regulations are found in 49 CFR (Title 49 of the Code of Federal Regulations).

The U.S. Occupational Safety and Health Administration (OSHA) regulates the handling of hazardous materials in the workplace as well as response to hazardous materials-related incidents, most notably through HAZWOPER (HAZ-ardous W-aste OP-erations and E-mergency R-esponse) regulations found at 29 CFR 1910.120.

The Environmental Protection Agency regulates hazardous materials as they may impact the community and environment, including specific regulations for environmental cleanup and for handling and disposal of waste hazardous materials.

The Consumer Product Safety Commission regulates hazardous materials that may be used in products sold for household and other consumer uses.

Hazard classes for materials in transport

Following the UN Model, the DOT divides regulated hazardous materials into nine classes, some of which are further divided into divisions. Hazardous materials in transportation must be placarded and have specified packaging and labelling. Some materials must always be placarded, others may only require placarding in certain circumstances.

Trailers of goods in transport are usually marked with a four digit UN (United Nations) number. This number can be referenced by first responders (Firefighters, Police Officers, and ambulance personnel) who can find information about the material in the Emergency Response Guidebook.

Fixed facilities

Different standards usually apply for handling and marking HAZMATs at fixed facilities, including NFPA 704 diamond markings (a consensus standard often adopted by local governmental jurisdictions), OSHA regulations requiring chemical safety information for employees, and CPSC requirements requiring informative labeling for the public, as well as wearing Hazmat suits when handling hazardous materials.

See also

External links

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