How Many Classes of Hazardous Materials Are There?

Hazardous materials, or “hazmat,” are substances that pose a risk to health, property, or the environment. The transportation, storage, and handling of these materials are strictly regulated to prevent accidents and ensure public safety. Hazardous materials are classified into nine distinct classes, each with specific characteristics and regulations. 

Read on to find out more about how hazardous materials are classified. 

Importance of Hazmat Classification

The classification of hazardous materials is vital for several reasons:

  • Safety: Classifying hazardous materials correctly reduces the risk of accidents when they are handled, stored, and transported.
  • Regulation Compliance: Compliance with national and international regulations, such as those from the Department of Transportation (DOT) in the United States or the International Maritime Organization (IMO), is mandatory for companies dealing with hazardous materials.
  • Emergency Response: By understanding the class of hazardous material involved in an incident, emergency responders can mitigate risks and protect public health.
  • Transportation: Different classes have specific labeling, packaging, and documentation requirements that must be followed during transportation to ensure safety.

Let’s get into the breakdown of the nine classes. 

Breakdown of Nine Classes of Hazardous Materials

Hazardous materials can be categorized into nine different classes as defined in 49 CFR 172.101 and 172. These include explosives, gases, liquids that are flammable or combustible, flammable solids, substances that are oxidizing, organic peroxides, substances that are toxic or infectious, radioactive materials, corrosives, and a miscellaneous category for other hazardous materials. Some of these classes have further subdivisions based on their specific chemical or physical properties.

Here is a brief description of each: 

Class 1- Explosives 

class 1 sign

These materials can detonate or explode under certain conditions. This often refers to fireworks, ammunition, and blasting agents. They are divided into six divisions based on their potential for explosion:

  • Division 1.1: Mass explosion hazard
  • Division 1.2: Projection hazard
  • Division 1.3: Fire, minor blast, or projection hazard
  • Division 1.4: Minor explosion hazard
  • Division 1.5: Very insensitive explosives with mass explosion hazard
  • Division 1.6: Extremely insensitive articles

Class 2- Gases 

class 2 sign

Flammable, toxic, or corrosive gases that can be compressed into containers fit into this category. This includes gases like propane, chlorine, and oxygen. Gases are further divided into three divisions:

  • Division 2.1: Flammable gases
  • Division 2.2: Non-flammable, non-toxic gases
  • Division 2.3: Toxic gases

Class 3- Flammable Liquids and Combustible Liquids

class 3 sign

These are liquids that readily ignite, like gasoline, diesel fuel, and paint. These are liquids with a flash point of 60°C (140°F) or lower. Other examples include acetone, kerosene, and alcohol. 

Class 4- Flammable Solids, Spontaneously Combustible, and Dangerous When Wet

class 4 sign

This class covers solids that can easily catch fire, ignite on their own, or dangerously react with water. Examples include matches, sodium, and calcium carbide. This category is further divided into three divisions: 

  • Division 4.1: Flammable solids
  • Division 4.2: Spontaneously combustible materials
  • Division 4.3: Dangerous when wet materials, emit flammable gases when in contact with water

Class 5- Oxidizer and Organic Peroxides

class 5 sign

This class includes materials that can accelerate the burning of other substances. Oxidizers are materials that can intensify combustion by releasing oxygen during a chemical reaction. Organic peroxides are compounds consisting of hydrogen peroxide and organic groups replacing one or both hydrogen atoms. This often refers to bleach, hydrogen peroxide, nitrates, ammonium nitrate fertilizers, and pool chemicals. This category is further divided into two divisions: 

  • Division 5.1: Oxidizing substances
  • Division 5.2: Organic peroxides, which are thermally unstable and can undergo exothermic decomposition

Class 6- Toxic (Poisonous) and Infectious Substances

class 6 sign

This class covers materials that can cause death, injury, or illness through ingestion, inhalation, or skin contact. It includes hazards like pesticides, arsenic, acids, dyes, chloroform, biomedical waste, and biohazardous materials. It is further divided into two divisions: 

  • Division 6.1: Toxic substances
  • Division 6.2: Infectious substances, which contain pathogens that can cause disease

Class 7- Radioactive Materials 

class 7 sign

This class includes materials that hold radionuclides– atoms with an unstable nucleus that undergo radioactive decay– where both the total activity and activity concentration surpass the set limit. These substances release ionizing radiation, which is a serious health risk. Radioactive materials commonly include medical isotopes, radioactive ores, depleted uranium, and density gauges. 

Class 8- Corrosive Materials

class 8 sign

This class includes materials that can cause severe damage or destruction to the skin, eyes, and other tissues it comes in contact with. They will also damage surrounding materials if they leak. Examples include acids, bases, batteries, paint, and lye.

Class 9- Miscellaneous Hazardous Materials

class 9 sign

Certain hazardous materials don’t fit into the initial eight categories. In such cases, they’re deemed as “miscellaneous hazardous materials,” a group that encompasses environmentally harmful substances, genetically altered organisms, substances transported at elevated temperatures, and magnetized materials. Some typical examples are dry ice, lithium-ion batteries, vehicles, first-aid kits, life-saving devices, and fuel cell engines.

Reporting Hazardous Materials Information 

hazardous placard colors
Image from: Safe Rack

Understanding these classifications is crucial for anyone who might encounter hazardous materials – from first responders to warehouse workers. Knowing the class of a hazardous material helps identify the specific dangers it poses and allows for a quick and appropriate response.

A variety of labels and placards exist for hazardous materials, each designed to instantly communicate the material type within a package or transport vehicle. Hazardous goods are transported worldwide in containers displaying the hazard classification prominently and using universally recognized designs and colors.

Besides the classification numbers, the color of hazmat placards is a key element for identification: 

  • Orange: indicates explosives like dynamite, ammunition, or fireworks.
  • Red: indicates flammable materials such as gasoline, rubbing alcohol, paint, or acetone.
  • Green: designates non-flammable substances like compressed or liquefied gases.
  • Yellow: represents oxidizers like ammonium nitrate, potassium nitrate, or nitric acid, which can combust in the presence of oxygen.
  • White: indicates poisonous and bio-hazardous substances such as dyes, aerosols, acids, and medical waste.
  • Blue: is assigned to substances that become flammable when in contact with water, like sodium, calcium, and potassium.
  • Half red and white sign: indicates substances that can ignite when exposed to air, like aluminum and lithium alkyls or white phosphorous.
  • Red and white stripes: signify flammable solids like matches and magnesium.
  • Red and yellow: are for organic peroxides that can ignite or explode, including methyl ethyl ketone peroxide and benzoyl peroxide.
  • Yellow and white: are used for radioactive substances often used in medical equipment.
  • Half white and half black: is for corrosive materials that can irritate and harm the skin, including batteries, hydrochloric acid, sulfuric acid, and sodium hydroxide.
  • White with black vertical stripes: indicates a range of dangerous goods, including nonclassified, environmentally hazardous substances like asbestos and dry ice.

If you work with hazardous materials, you must understand these classifications for your safety and the safety of others. 

Non-hazardous and Hazardous Waste Removal 

AllSource Environmental is a national material & waste management company that provides unique solutions for all of your environmental needs and services. Our experienced and professional personnel can assist you with all of your regulated and non-regulated waste streams and industrial services.

Reach out today to take advantage of our complimentary on-site audit service. One of our experts will evaluate your current state and present you with a comprehensive report outlining cost-saving opportunities, detailing every step of the process. Additionally, check out the services we provide here