标题：The Nine Major Categories of Hazardous Materials
Article
Hazardous materials are substances or objects that pose a threat to public safety, health, and the environment. They are categorized based on the type of risk they present and the potential consequences of an incident involving them. Here's an overview of the nine major categories of hazardous materials, along with their definitions and relevant information sources:
1. Explosives
Definition: Substances that can cause a rapid chemical reaction resulting in an explosion.
Source: The United Nations Economic Commission for Europe (UNECE) defines explosives as substances or mixtures that are designed to detonate, deflagrate, or produce an explosive reaction under the influence of heat, shock, friction, or other initiating conditions.
[Read more](https://www.unece.org/fileadmin/DAM/trans/tdg/pdf/tdg2007_part1_en.pdf)
2. Gases
Definition: Substances under pressure that can cause fire or explosion or be harmful to humans.
Source: The U.S. Department of Transportation (DOT) categorizes gases as compressed,液化，or dissolved under pressure.
[Read more](https://www.transportation.gov/safety/hazmat/regshazmatclassification)
3. Flammable Liquids
Definition: Substances having a flash point below 93.5 degrees Celsius (200 degrees Fahrenheit) and a vapor pressure of 101.3 kPa (15.0 psi) or more at 20 degrees Celsius (68 degrees Fahrenheit).
Source: The International Air Transport Association (IATA) provides guidelines for the classification of flammable liquids.
[Read more](https://www.iata.org/en/publications/regulations/safetyregulationsdangerousgoods/ti1/)
4. Flammable Solids
Definition: Substances that are liable to spontaneous combustion or can be ignited by friction, shock, or other means.
Source: The International Maritime Organization (IMO) provides the guidelines for the classification of flammable solids.
[Read more](https://www.imo.org/en/OurWork/StandardsAndGuidelines/Pages/DangerousGoods.aspx)
5. Oxidizing Substances and Organic Peroxides
Definition: Substances that supply oxygen to support combustion or substances that are readily capable of forming explosive compounds by mixing with oxygen.
Source: The DOT regulations classify oxidizing substances and organic peroxides based on their specific properties.
[Read more](https://www.transportation.gov/safety/hazmat/regshazmatclassification)
6. Poisonous and Infectious Substances
Definition: Substances that are known to be harmful to humans and animals, including infectious substances.
Source: The World Health Organization (WHO) provides guidelines for the classification of poisonous and infectious substances.
[Read more](https://www.who.int/ith/dangerous_substances/en/)
7. Radioactive Materials
Definition: Materials that emit ionizing radiation.
Source: The International Atomic Energy Agency (IAEA) provides regulations and guidelines for the transport of radioactive materials.
[Read more](https://www.iaea.org/publications/Booklets/RegulatoryTransportOfRadioactiveMaterials)
8. Corrosive Substances and Materials
Definition: Substances that cause damage to living tissue, metals, or other materials.
Source: The DOT regulates the transportation of corrosive substances and materials.
[Read more](https://www.transportation.gov/safety/hazmat/regshazmatclassification)
9. Miscellaneous Hazardous Materials
Definition: A catchall category for hazardous materials that do not fit into the other categories.
Source: The DOT and other regulatory bodies provide detailed guidelines for this category.
[Read more](https://www.transportation.gov/safety/hazmat/regshazmatclassification)
Common Questions and Answers
1. What is the difference between hazardous materials and dangerous goods?
Hazardous materials and dangerous goods are often used interchangeably, but "hazardous materials" is the more common term in the United States, while "dangerous goods" is used more frequently internationally.
2. How are hazardous materials classified?
Hazardous materials are classified based on their physical, chemical, and health hazards according to international and national regulations.
3. Are all hazardous materials considered dangerous goods?
Not necessarily. While all dangerous goods are hazardous materials, not all hazardous materials are classified as dangerous goods for transportation purposes.
4. What is the flash point of a flammable liquid?
The flash point of a flammable liquid is the lowest temperature at which it can ignite in the presence of an ignition source.
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