Classification

Scope

Hazardous materials must be properly classified by the shipper or offeror before the shipment is offered for transportation.

Regulatory citations

• 49 CFR 173.115 — Class 2, Divisions 2.1, 2.2, and 2.3 — Definitions
• 49 CFR 173.116 — Class 2 — Assignment of hazard zone
• 49 CFR 173.120 — Class 3 — Definitions
• 49 CFR 173.121 — Class 3 — Assignment of packing group
• 49 CFR 173.124 — Class 4, Divisions 4.1, 4.2, and 4.3 — Definitions
• 49 CFR 173.125 — Class 4 — Assignment of packing group
• 49 CFR 173.127 — Class 5, Division 5.1 — Definition and assignment of packing groups
• 49 CFR 173.128 — Class 5, Division 5.2 — Definitions and types
• 49 CFR 173.132 — Class 6, Division 6.1 — Definitions
• 49 CFR 173.133 — Assignment of packing group and hazard zones for Division 6.1 materials
• 49 CFR 173.134 — Class 6, Division 6.2 — Definitions and exceptions
• 49 CFR 173.136 — Class 8 — Definitions
• 49 CFR 173.137 — Class 8 — Assignment of packing group
• 49 CFR 173.140 — Class 9 — Definitions
• 49 CFR 173.141 — Class 9 — Assignment of packing group
• 49 CFR 173.144 — Other Regulated Material (ORM) — Definitions
• 49 CFR 173.2 — Hazardous materials classes and index to hazard class definitions
• 49 CFR 173 Subpart C — Definitions, Classification and Packaging for Class 1

Key definitions

• Combustible liquid: Any liquid that does not meet the definition of any other hazard class and has a flash point above 60°C (140°F) and below 93°C (200°F). The classification of a material as a “combustible liquid” is strictly for transportation within the United States and is not recognized internationally.
• Corrosive material: A liquid or solid that causes irreversible damage to human skin at the site of contact within a specified period of time, or a liquid (or a solid which may become a liquid during transportation) that has a severe corrosion rate on steel or aluminum, based on the criteria in 173.137(c)(2).
• Explosive: Any substance or article, unless otherwise classified, that is:
  • Designed to function by explosion, or
  • Which, by chemical reaction within itself, is able to function in a similar manner even if not designed to function by explosion.
• Flammable liquid:
  • Any liquid having a flash point of not more than 60°C (140°F); or
  • Any material in a liquid phase with a flash point at or above 37.8°C (100°F) that is intentionally heated and offered for transportation, or transported at or above its flash point in a bulk packaging.
• Hazardous material: A substance or material that the Secretary of Transportation has determined is capable of posing an unreasonable risk to health, safety, and property when transported in commerce, and has designated as hazardous under section 5103 of Federal hazardous materials transportation law (49 U.S.C. 5103). The term includes hazardous substances, hazardous wastes, marine pollutants, elevated temperature materials, materials designated as hazardous in the Hazardous Materials Table (see 49 CFR 172.101), and materials that meet the defining criteria for hazard classes and divisions in Part 173 of the hazardous materials regulations (HMR).
• Mass explosion: An explosion that affects almost the entire load instantaneously.
• Pathogen: A microorganism (including bacteria, viruses, rickettsiae, parasites, fungi) or other agent, such as a proteinaceous infectious particle (prion), that can cause disease in humans or animals.
• Radioactive material: Any material containing radionuclides where both the activity concentration and total activity in the consignment exceed the values in 173.436 or 173.433.
• Shipper (person who offers or offeror): Anyone who does either or both of the following:
  • Performs, or is responsible for performing, any pre-transportation function required under the hazardous material regulations in commerce; or
  • Tenders or makes the hazardous material available to a carrier for transportation in commerce.

Summary of requirements

Shipper responsibilities. The shipper must determine whether the material being offered for transportation has the characteristics of one or more of the hazard classes defined in the “Hazardous Materials Regulations” (HMR) of the U.S. Department of Transportation (DOT). In doing this, the shipper is assisted by the Hazardous Materials Table (HMT) found in 172.101, which lists many materials considered hazardous in alphabetical order by their proper shipping name.

It must be emphasized, however, that a material may not be listed by name in the table, and may still be subject to the Hazardous Materials Regulations, in which case the name most accurately describing the material shall be used. In addition, some materials listed in the table may not be subject to these regulations because of such factors as the quantity to be transported and the transportation mode to be used. Furthermore, a material may be listed in the table but the material being shipped does not meet the hazard class indicated in Column 3, therefore it is not regulated, assuming it meets the definition of no other hazard class.

Hazmat classification guidelines. The regulations discuss and define hazardous materials according to the classification scheme below:

Class 1 (Explosive) Materials
Class 2 (Gas) Materials
Class 3 (Flammable Liquid) Materials
Class 4 (Flammable Solid, Spontaneously Combustible, Dangerous When Wet) Materials
Class 5 (Oxidizing & Organic Peroxide) Materials
Class 6 (Poisonous) Materials
Class 7 (Radioactive) Materials
Class 8 (Corrosive) Materials
Class 9 (Miscellaneous) Materials

The sections below offer general guidelines for classifying the material to be shipped. Consult the specific regulations for full specifications covering each type of hazardous material.

Class 1 (explosive) materials has six divisions:

• Division 1.1 consists of explosives that have a mass explosion hazard.
• Division 1.2 consists of explosives that have a projection hazard but not a mass explosion hazard.
• Division 1.3 consists of explosives that have a fire hazard and either a minor blast hazard or a minor projection hazard or both, but not a mass explosion hazard.
• Division 1.4 consists of explosives that present a minor explosion hazard. The explosive effects are largely confined to the package, and no projection of fragments of appreciable size or range is to be expected. An external fire must not cause virtually instantaneous explosion of almost the entire contents of the package.
• Division 1.5 consists of very insensitive explosives that have a mass explosion hazard, but they are so insensitive that they offer very little probability of initiation or of transition from burning to detonation, under normal transport conditions.
• Division 1.6 consists of extremely insensitive articles that lack a mass explosive hazard. This division is comprised of articles that predominately contain extremely insensitive substances and that demonstrate a negligible probability of accidental initiation or propagation.

Class 2 (gas) materials has three divisions:

• Division 2.1 includes any material that is a gas at 20°C (68°F) or less and 101.3 kPa (14.7 psia) of pressure, and that:
  • Is ignitable at 101.3 kPa (14.7 psia) when in a mixture of 13 percent or less by volume with air, or
  • Has a flammable range at 101.3 kPa (14.7 psia) with air of at least 12 percent, regardless of the lower limit.
• Division 2.2 materials are non-flammable, non-poisonous compressed gases including compressed gas, liquefied gas, pressurized cryogenic gas and compressed gas in solution. They include any material or mixture that:
  • Exerts in the packaging a gauge pressure of 200 kPa (29.0 psig/43.8 psia) or greater at 20°C (68°F), is a liquefied gas or is a cryogenic liquid, and
  • Does not meet the definition of Division 2.1 and 2.3.
• Division 2.3 materials are gases that are poisonous by inhalation and are:
  • Known to be so toxic to humans that they pose a health hazard during transportation; or
  • In the absence of adequate data on human toxicity, are presumed toxic to humans because when tested on laboratory animals they have an LC₅₀ value of not more than 5000 mL/m³.

Class 3 (flammable liquid) materials.173.120(b)(2) allows Class 3 (flammable) liquids with flash points at or above 38°C (100°F) that do not meet the definition of any other hazard class, to be reclassified as “combustible liquids” for transportation by highway and rail. For shipments involving any air, water or international movement, these materials are Class 3 (flammable) materials.An elevated temperature material that meets the definition of a Class 3 material, because it is heated at or above its flashpoint, may not be reclassified as a combustible liquid.

Class 4 (flammable solid, spontaneously combustible, dangerous when wet) materials has three divisions:

• Division 4.1 (flammable solid) material includes:
  • Desensitized explosives that when dry are explosives of Class 1, other than those of compatibility group A, which when wetted with sufficient water, alcohol, or plasticizer to suppress the explosive properties, and materials specifically authorized by name in the HMT or by the Associate Administrator for Hazardous Materials Safety.
  • Self-reactive materials that are thermally unstable and that can undergo a strong exothermal decomposition even without oxygen (air).
  • Readily combustible solids that may cause a fire through friction, show a burning rate faster than 2.2 mm (0.087 inches) per second under specified UN test procedures, or any metal powders that can be ignited and react over the whole length of a sample in 10 minutes or less under specified UN test procedures.
  • Polymerizing materials without stabilization, are liable to undergo an exothermic reaction resulting in the formation of larger molecules or resulting in the formation of polymers under conditions normally encountered in transport.
• Division 4.2 (spontaneously combustible) material includes:
  • A pyrophoric material, liquid or solid, that even in small quantities and without an external ignition source, can ignite within five minutes after coming in contact with air under specified UN test procedures.
  • A self-heating material that, when in contact with air generates heat that may lead to self-ignition and combustion. Exhibits spontaneous ignition or if the temperature of the sample exceeds 200°C (392°F) during a 24-hour test period under specified UN test procedures.
• Division 4.3 (dangerous when wet) material is one that:
  • By contact with water is liable to become spontaneously flammable; or
  • Gives off flammable or toxic gas at a rate greater than 1 liter per kilogram of material per hour, under specified UN test procedures.

Class 5 (oxidizer and organic peroxide) materials has two divisions:

• Division 5.1 (oxidizer) material is a material that may, generally by yielding oxygen, cause or enhance the combustion of other materials.
• Division 5.2 (organic peroxide) material is any organic compound containing oxygen (O) in the bivalent -O-O- structure that may be considered a derivative of hydrogen peroxide, where one or more of the hydrogen atoms have been replaced by organic radicals, with some exceptions.

Class 6 (poisonous) materials has two divisions:

• Division 6.1 materials are those materials, other than gases, that:
  • Are known to be so toxic to humans as to afford a hazard to health during transportation; or
  • In the absence of adequate data on human toxicity are presumed to be toxic to humans because they fall within specified oral, dermal or inhalation toxicity ranges when tested on laboratory animals, or are irritating materials, with properties similar to tear gas, which cause extreme irritation, especially in confined spaces.
• Division 6.2 materials are known to contain a pathogen or are reasonably expected to contain a pathogen.

Class 7 (radioactive) materials.Class 7 materials contain radionuclides where both the activity concentration and the total activity in the consignment exceed:

• The values specified in the table in 173.436, or
• The values derived according to the instructions in 173.433.

Class 8 (corrosive) materials. Corrosive materials, as defined above, cause irreversible damage to human skin or have a severe corrosion rate on steel or aluminum.

Class 9 (miscellaneous) materials. Miscellaneous hazardous materials present a hazard during transportation but do not meet the definition of any other hazard class. These include:

• Any materials that have an anesthetic, noxious or other similar property which could cause extreme annoyance or discomfort to a flight crew member to prevent the correct performance of assigned duties; or
• Any materials that meet the definition in 171.8 for an elevated temperature material, a hazardous substance, a hazardous waste, or a marine pollutant.