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How Many Classes of Hazardous Materials are there?

April 12, 2023

Whether by plane, truck, train, or boat, there are strict labeling and storage requirements for hazardous waste transportation disposal, courtesy of the DOT. This blog entry discusses one of the most important of those requirements: classification of hazardous materials and how many classes of hazardous materials are there. Q&As include:

1. How many classes of hazardous waste are there?

2. Why is hazardous waste classification important?

3. What is Class 1 Explosives Hazardous Waste?

4. What are Class 2 Gasses?

5. What are Class 3 Flammable Liquids?

6. What are Class 4 Flammable Solids?

7. What are Class 5 Oxidizing Substances & Organic Peroxides?

8. What are Class 6 Toxic or Infectious Substances?

9. What are Class 7 Radioactive Materials?

10. What are Class 8 Corrosive Materials?

11. What is Class 9 Miscellaneous Hazardous Waste?

12. Where can you get further guidance about DOT hazmat classifications?

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1. How many classes of hazardous waste are there?

There are nine classes of hazardous waste. These are:

  1. Explosives (See Q.3)

  2. Gases (See Q.4)

  3. Flammable Liquids (See Q.5)

  4. Flammable Solids (See Q.6)

  5. Oxidizing Substances & Organic Peroxides (See Q.7)

  6. Toxic or Infectious Substances (See Q.8)

  7. Radioactive Material (See Q.9)

  8. Corrosives (See Q.10)

  9. Miscellaneous (See. Q.11)

2. Why is hazardous waste classification important?

Classification is important because it informs transporters about what procedures to follow and precautions to take for a particular kind of hazmat in transit. And in case of an accident, clear hazmat classification and hazardous labeling ensure that environmental, waste management, and emergency personnel know what they’re dealing with.

3. What is Class 1 Explosives Hazardous Waste?

This includes any explosive substances, articles, or devices that explode—either intentionally or by accident. Each is subclassed into one of six divisions based upon the relative degree of danger it poses and the predominant kind of hazard it presents: destructive shockwave, fire hazard, and/or projectile emission. 

The first three categories are the most dangerous. They are:

1.1.  Mass explosion hazards. These tend to explode instantly with destructive force. E.g., nitroglycerine, mercury fulminate (used in blasting caps), and certain kinds of fireworks.

1.2. Projection hazards. These emit shrapnel and/or other dangerous projectiles with explosive force. E.g., ammunition and grenades.

1.3. Fire hazards. Pyrotechnic flash powders for fireworks are a common example here, as well as some liquid and solid propellants. 

You can enjoy a fuller explanation of Class I explosives here. Meanwhile, we’ll only give passing mention to the remaining four categories, as they have less potential for causing any eruptive mayhem. They are:

1.4.  Package-confined hazards

1.5.  Insensitive-substance hazards 

1.6.  Extremely insensitive-substance hazards

4. What are Class 2 Gasses?

There are three kinds:

  1. Flammable gasses are in a gaseous state at 68°F and burn readily in the air. (e.g., propane and spray paints).

  2. Non-flammable gases include liquified gases or cryogenic liquids (e.g., helium and asthma inhalers).

  3. Poisonous gases are toxic to humans or presumed to be so (e.g., carbon monoxide).

5, What are Class 3 Flammable Liquids?

The flash point of flammable liquids is 140°F or less, which is the temperature at which a nearby ignition source can ignite its vapors. E.g., gasoline, kerosene, acetone, ethanol, xylene, as well as many paints and common solvents.

6. What are Class 4 Flammable Solids?

These are the three subclasses of flammable solids: 

4.1. Flammable solids (e.g., matchsticks)

4.2. Spontaneously combustible material (e.g., oily rags) (See autoignition temperature)

4.3. Dangerous when wet (e.g., magnesium fire starter)

7. What are Class 5 Oxidizing Substances & Organic Peroxides?

There are two subclasses:

5.1. Oxidizing Substances or oxidizers can contribute to the combustion of other materials (e.g., concentrated hydrogen peroxide or silver nitrate).

5.2. Organic Peroxides are a combination of oxidizer and organic fuels. As such, they are thermally unstable and prone to releasing dangerous amounts of heat and energy. The most common is peroxyacetic acid (PAA), which is used as an industrial bleach, as a bactericide and fungicide in food processing, and as a catalyst for epoxy resins.

8. What are Class 6 Toxic or Infectious Substances?

There are two subclasses of these toxic or infectious substances:

6.1. Toxic or Poisonous Material include solids or liquids known or presumed to be toxic to humans by way of oral, dermal, and/or inhalation exposure. Some medications fall into this category when presented in high doses (e.g., the blood-thinner Coumadin).

6.2. Infectious Substances include materials known or reasonably expected to be     pathogenic.

9. What are Class 7 Radioactive Materials?

Uranium and plutonium are the most obvious candidates here. But exit signs, smoke detectors, and x-ray equipment are also common sources of radioactive material and can turn into radioactive waste.

10. What are Class 8 Corrosive Materials?

Per the EPA, these corrosive materials are liquids or solids that cause full-thickness destruction of human skin at the site of contact within a specified period of time. You can read more about corrosive chemicals here.

11. What is Class 9 Miscellaneous Hazardous Waste?

Whatever doesn’t fit into one of the hazardous material classes 1 thru 8 is deemed Class 9. This is because, while Classes 1-thru-8 have specific definitions relative to the hazards they present (e.g., flashpoints, rates of corrosion, lethal dosages, etc.), Class 9 parameters are purposefully imprecise.

Thereby, Class 9 restrictions can potentially burden many materials that are not normally subject to hazardous waste regulations. (It’s notable that no hazardous waste can be properly categorized as Class 9 and simultaneously as any one of Classes 1-thru-8.) 

12. Where can you get further guidance about DOT hazmat classifications?

The experience, knowledge, and technical resources of a reputable hazardous waste management company are essential to keeping you safe and legal.

Hazardous Waste Experts specializes in providing you with experienced, properly licensed personnel to ensure that all your consumer and commercial wastes are accurately segregated for hazmat classification—as well as provide proper hazardous waste transportation and ultimately disposed of—in complete compliance with federal, state, and local standards. 

Get expert advice today. And thank you for reading our blog!

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