Hazmat Placards and UN Numbers: What You Need to Know

Have you ever seen a truck, railcar, container or large tanks at a tank farm and wondered what types of chemicals it was transporting or storing? The answer can be found in its UN numbers and hazmat placards, which indicate the applicable classifications and handling requirements for the chemicals.

Introduction to Hazardous Substances

Hazardous substances are materials that pose a significant risk to human health, safety, and the environment. These substances can take various forms, including chemicals, toxic substances, and environmentally hazardous substances. The transportation of hazardous substances requires special precautions to ensure safe handling and prevent accidents. In the realm of international commerce, the United Nations (UN) plays a crucial role in regulating the transport of hazardous substances through its recommendations and guidelines.

The UN assigns unique four-digit numbers, known as UN numbers, to identify and classify hazardous substances. These numbers are essential for determining the proper shipping names, packing groups, and compatibility groups for hazardous substances. By using these UN numbers, shippers can ensure that hazardous substances are transported safely and in compliance with international regulations. This system helps to identify dangerous goods and ensures that they are handled with the appropriate care to protect human health, safety, and the environment.

What Are UN Numbers?

Located on the back or sides of trailers or other containers, UN numbers (or UN IDs) are four-digit numbers ranging from 0004-3534 that identify dangerous goods or hazardous substances — such as explosives, flammable liquids, or toxic substances — in the framework of international transport. These four-digit numbers are essential for identifying the specific hazards associated with each substance.

These numbers are assigned by the United Nations (UN) Committee of Experts on the Transport of Dangerous Goods, and must be listed on the Material Safety Data Sheet (MSDS) of each shipment. While some hazardous materials share a common UN number due to similar properties, others have different UN numbers to specify unique hazards. (Goods that aren’t classified or regulated by the UN are given four-digit North American (NA) numbers ranging from 8000-9279. These numbers are designated by the United States Department of Transportation (DOT).)

What Are Hazmat Placards?

In addition to a UN number, the DOT requires cargo to carry Hazmat placards that help shippers determine its class, division, and compatibility group.

Similar to road or construction signs, these diamond-shaped hazmat placards alert the public that potentially hazardous materials are being hauled, as well as inform emergency responders which chemicals are present in case of an accident. Each placard indicates the hazard class of the material, which is crucial for ensuring proper handling and emergency response. Even if members of the public or first responders are unaware of exactly which materials are on board, the presence of hazmat placards lets them know that they should proceed with caution.

With rare exceptions, companies that transport hazardous materials without the use of DOT hazmat placards are at risk for stiff fines and other penalties.

UN Hazmat Sign Components and Classifications

It’s vital that anyone who works with or around hazardous materials can properly identify the various aspects of each hazmat placard, as well as the various classifications that each one represents.

Proper identification of hazardous materials through UN numbers is essential for ensuring safety and compliance with regulations.

CLASSIFICATIONS

Hazmat warning placards are broken down into nine different classifications, along with their divisions. Each class number is found at the bottom of the sign, while the division number can be found in the middle.

These classifications also apply to articles, such as batteries, that pose specific risks and require proper identification and handling.

COMPONENTS

Each hazmat sign has up to six main parts:

1. Hazard classification number — See below.
2. UN/NA number — See above.
3. Compatibility letters — Some placards include the letters A-S, which let shippers and carriers know which explosive materials can be loaded together onto a trailer.
4. Color — Other than classification numbers, hazmat placards are most easily identified by their different colors.

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

Each hazmat sign has up to six main parts, which are crucial for the safe transport of packages containing hazardous materials.

1. Words — Depending on the contents of each container, its hazmat placard is labeled with various terms like “Spontaneously Combustible,” “Explosive,” “Nonflammable Gas,” “Oxygen,” “Poison,” “Flammable,” and others.
2. Graphics — Different hazmat placards feature illustrations to reinforce the danger of their contents. For example, placards for toxic materials include an image of a skull and crossbones, while signs for radioactive materials include a radiation symbol consisting of three blades surrounding a small circle.

Proper packaging is essential to ensure that each package is marked and labeled according to regulatory requirements.

Rules for Placement

According to federal regulations, each freight container, railcar, transport vehicle, or other vessel carrying hazardous materials must display placards on each side and each end. Regulations also state that placards on railcars and transport vehicles must be clearly visible from the direction they face unless they are obscured when coupled with another railcar or transport vehicle.

For detailed information on placard placement, refer to the relevant page in the regulatory guide.

In all, carriers must display at least four placards in areas where the view isn’t obstructed. Some carriers add extra signs on each side of the truck cab for additional visibility.

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Transport Requirements

The transport of hazardous substances is governed by specific rules and regulations designed to ensure safe transportation and prevent accidents. Shippers must adhere to these regulations, which vary depending on the mode of transport, such as air, land, or sea. For instance, the transportation of hazardous substances by air is regulated by the International Air Transport Association (IATA), while the International Maritime Organization (IMO) oversees transportation by sea.

Using proper shipping names, UN numbers, and placards is crucial for identifying and handling hazardous substances during transportation. These identifiers help ensure that everyone involved in the transport process is aware of the potential hazards and can take the necessary precautions. Additionally, shippers must ensure that their shipping containers are properly marked and labeled to indicate the presence of hazardous substances. This includes displaying the appropriate placards and ensuring that all markings are clearly visible and legible.

Model Regulations and Guidelines

The United Nations Recommendations on the Transport of Dangerous Goods, commonly known as the “Orange Book,” provide model regulations and guidelines for the transportation of hazardous substances. These recommendations are widely adopted by countries and international organizations to ensure consistency and safety in the transportation of hazardous substances.

The model regulations cover various aspects of hazardous substance transportation, including classification, packaging, marking, and documentation. They provide detailed information on the use of UN numbers, proper shipping names, and placards to identify and handle hazardous substances. Additionally, the guidelines address the transportation of specific types of hazardous substances, such as flammable liquids, explosives, and radioactive substances.

By following these guidelines, shippers can ensure that their hazardous substances are transported safely and in compliance with international regulations. The model regulations help to standardize the transport of dangerous goods, making it easier for shippers to navigate the complex requirements and ensure the safety of their shipments.

Common chemical transportation placards.

Acetic Acid

Acetic Acid handling design & loading

Acetic Anhydride

Acetic Anhydride handling design & loading

Acetonitrile

Acetonitrile handling design & loading

Acrolein

Acrolein handling design & loading

Acrylic Acid

Acrylic Acid handling design & loading

Acrylonitrile

Acrylonitrile handling design & loading

Aluminum Chloride

Aluminum Chloride handling design & loading

Aluminum Sulfate

Aluminum Sulfate handling design & loading

Ammonia

Ammonia handling design & loading

Ammonium Hydroxide

Ammonium Hydroxide handling design & loading

Ammonium Nitrate

Ammonium Nitrate handling design & loading

Aniline

Aniline handling design & loading

Benzene

Benzene handling design & loading

Benzyl Chloride

Benzyl Chloride handling design & loading

Bromotrifluoro methane

Bromotrifluoromethane handling design & loading

Butadiene

Butadiene handling design & loading

Carbon Dioxide

Carbon Dioxide handling design & loading

Caustic

Caustic handling design & loading

Chlorine

Chlorine handling design & loading

Chloroform

Chloroform handling design & loading

Chlorosulfonic Acid

Chlorosulfonic Acid handling design & loading

DMH

Dimethylformamide handling design & loading

Diethylene Glycol

Diethylene Glycol handling design & loading

Dodecylbenzene Sulfonic Acid

Dodecylbenzene Sulfonic Acid handling design & loading

Ethanol

Ethanol handling design & loading

Ethyl Acetate

Ethyl Acetate handling design & loading

Ethyl Chloride

Ethyl Chloride handling design & loading

Ethylene

Ethylene handling design & loading

Ethylene Dichloride

Ethylene Dichloride handling design & loading

Ethylene Oxide

Ethylene Oxide handling design & loading

Ethylene Glycol

Ethylene Glycol handling design & loading

Ferric Chloride

Ferric Chloride handling design & loading

Ferrous Chloride

Ferrous Chloride handling design & loading

Hexane

Hexane handling design & loading

Hydrochloric Acid

Hydrochloric Acid handling design & loading

Hydrofluoric Acid

Hydrofluoric Acid handling design & loading

Hydrofluorosilicic Acid

Hydrofluorosilicic Acid handling design & loading

Hydrogen Cyanide

Hydrogen Cyanide handling design & loading

Hydrogen Peroxide

Hydrogen Peroxide handling design & loading

Hydrofluoric Acid

Hydrofluoric Acid handling design & loading

Isopropyl Acetate

Isopropyl Acetate handling design & loading

Liquid Argon

Liquid Argon handling design & loading

Liquid Nitrogen

Liquid Nitrogen handling design & loading

Liquid Oxygen

Liquid Oxygen handling design & loading

Maleic Anhydride

Maleic Anhydride handling design & loading

Methanol

Methanol handling design & loading

Methyl Chloride

Methyl Chloride handling design & loading

Methyl Isocyanate

Methyl Isocyanate handling design & loading

Methyl Ethyl Ketone

Methyl Ethyl Ketone handling design & loading

Methyl Methacrylate

Methyl Methacrylate handling design & loading

Molten Sulphur

Molten Sulphur handling design & loading

MDI

MDI handling design & loading

Nitric Acid

Nitric Acid handling design & loading

Oleum

Oleum handling design & loading

Phenol

Phenol handling design & loading

Phosphoric Acid

Phosphoric Acid handling design & loading

Phosphorus Oxychloride

Phosphorus Oxychloride handling design & loading

Phosphorus Trichloride

Phosphorus Trichloride handling design & loading

Polypropylene

Polypropylene handling design & loading

Renewable Diesel

Renewable Diesel handling design & loading

Sodium Cyanide

Sodium Cyanide handling design & loading

Sodium Hypochlorite

Sodium Hypochlorite handling design & loading

Sodium hydroxide

Sodium hydroxide handling design & loading

Styrene Monomer

Styrene Monomer handling design & loading

Sulfuric Acid

Sulfuric Acid handling design & loading

Sulfur Dioxide

Sulfur Dioxide handling design & loading

Titanium Tetrachloride

Titanium Tetrachloride handling design & loading

Toluene

Toluene handling design & loading

Toluene Diisocyanate

Toluene Diisocyanate handling design & loading

Turpentine

Turpentine handling design & loading

UAN (Urea Ammonium Nitrate)

UAN handling design & loading

UREA

UREA handling design & loading

Vinyl Acetate

Vinyl Acetate handling design & loading

Vinyl Chloride

Vinyl Chloride handling design & loading

Xylene

Xylene handling design & loading

Zinc Chloride

Zinc Chloride handling design & loading