Appendix D 

Hazardous Materials Definitions

Aerosol means any nonrefillable metal receptacle containing a gas that is compressed, liquified, or dissolved under pressure, the sole purpose of which is to expel a nonpoisonous (other than a Division 6.1 Packing Group III material) liquid, paste, or powder and fitted with a self-closing release device allowing the contents to be ejected by the gas.

Air transportation requirements apply to all mailable hazardous materials sent at Priority Mail Express, Priority Mail, First-Class Mail, or First-Class Package Service prices for domestic shipments, or Priority Mail Express International, Priority Mail International, First-Class Mail International, and First-Class Package International Service prices for international shipments. All mailable hazardous materials sent at those prices must meet the requirements that apply to air transportation. Mailable hazardous materials sent at any of those prices may or may not be transported via air depending on the distance between the point of origination and the point of destination, and the ability of the USPS to obtain an air carrier between those points.

Ammunition includes all kinds of bombs, grenades, rockets, mines, projectiles, and other similar devices or contrivances. Ammunition is a Class 1 explosive and is nonmailable.

ASTM refers to the American Society for Testing and Materials.

Batteries, dry are sealed, nonvented batteries of the type used in flashlights or for the operation of small household apparatus. They contain zinc salts and other solids, or may be of the nickel cadmium type or other combinations of metals.

Biohazard is a biological material that poses a threat to humans or the environment. The biohazard symbol that is required for certain Division 6.2 materials is an OSHA requirement detailed in 29 CFR 1910.1030.

Biological products means a material derived from a living organism that is prepared and manufactured in accordance with 9 CFR 102-104 (licenses for biological products; experimental products, distribution, and evaluation prior to licensing; and permits for biological products), 21 CFR 312 (investigational new drug application), or 21 CFR 600-680 (biologics) and that, under such provisions, may be shipped in interstate commerce. Biological products include, but are not limited to, products such as vaccines.

Btu means British thermal unit.

C means degrees Celsius or Centigrade. Celsius or Centigrade is a thermometer scale on which the freezing and boiling points of water are divided into 100, with 0° representing the freezing point and 100° the boiling point.

Cargo aircraft only means an aircraft that is used to transport cargo and is not engaged in carrying passengers.

Ci means curie.

Clinical (diagnostic) specimen is any human or animal material including, but not limited to, excreta, secreta, blood, blood components, tissue, and tissue fluids that have been collected and are being mailed to a medical or forensic laboratory for the purpose of diagnosis, or being mailed from a medical or forensic laboratory for return to a law enforcement agency.

Combination packaging means one or more inner packagings (i.e., receptacles) secured in a nonbulk outer packaging. This is a term used by DOT in 49 CFR.

Combustible liquid is a Class 3 material in a liquid form that has a flashpoint above 140° F (60° C) and below 200° F (93° C).

Compatibility group refers to a designated alphabetical letter used to categorize different types of Class 1 explosive substances and articles for purposes of safe stowage and segregation (e.g., Division 1.4S).

Composite packaging consists of an outer packaging and an inner receptacle so constructed that they form an integral unit. Once assembled, it remains a single integrated unit; it is filled, stored, shipped, and emptied as such. This is a term used by DOT in 49 CFR.

Compressed gas is a material or mixture within a container that is a gas at 68° F (20° C) or less and 14.7 psi (101.3 kPa), or exerts an absolute pressure of 40.6 psia (280 kPa) or greater at 68° F (20° C). Gases are Class 2 hazardous materials.

Consumer commodity is a hazardous material that is packaged and distributed in a quantity and form intended or suitable for retail sale and designed for individual consumption for personal care or household use purposes. This term can also include certain drugs or medicines.

Corrosive material means a Class 8 liquid or solid material that causes visible destruction of human skin at the site of contact within a specified period of time. A liquid that has a severe corrosion rate on steel or aluminum is also a corrosive material.

Dangerous goods is the term used to describe hazardous materials shipped in international commerce.

Dangerous when wet material is a Division 4.3 material that by contact with water is liable to become spontaneously flammable or to give off flammable or toxic gas.

De minimis is the maximum quantity of Packing Group II & III in Class 3, Division 4.1, Division 4.2, Division 4.3, Division 5.1, Division 6.1, Class 8, and Class 9 materials that do not meet the definition of hazardous material. Inner receptacles or articles are limited to One (1) ml (0.03 ounce) for liquids; and One (1) gram (0.04 ounce) for solid materials and 100 ml (3.38 ounces) for liquids; and 100 g (0.22 pounds) for solid materials total aggregate per mailpiece. De minimis does not apply to prohibited items (e.g., mercury, hydrofluoric acid).

Designated facility is (for EPA purposes) the hazardous waste treatment, storage, or disposal facility that has been designated on a hazardous waste manifest by the waste generator.

Diagnostic specimen, see clinical specimen.

Division refers to a subpart of a hazard class (e.g., Division 6.1).

DOD refers to the U.S. Department of Defense.

Domestic transportation is transportation between locations within the United States.

DOT refers to the U.S. Department of Transportation. DOT has the federal authority to regulate the transportation of hazardous materials within domestic commerce. DOT regulations are codified in Title 49, Code of Federal Regulations (49 CFR).

Elevated temperature material means a material that, when offered for transportation, is in a liquid phase and at a temperature at or above 212° F (100° C); is in a liquid phase with a flashpoint at or above 100° F (37.8° C) that is intentionally heated and offered for transportation at or above its flashpoint; or is in a solid phase and at a temperature at or above 464° F (240° C). Elevated temperature materials are Class 9 hazardous materials and are nonmailable.

EPA refers to the U.S. Environmental Protection Agency. EPA regulations are codified in Title 40, Code of Federal Regulations (40 CFR).

Etiologic agent, see infectious substance.

Explosive is any Class 1 substance or article, including a device, that is designed to function by explosion (i.e., an extremely rapid release of gas and heat) or that, by chemical reaction within itself, is able to function in a similar manner.

F means degrees Fahrenheit. Fahrenheit is a thermometer scale on which the boiling point of water is 212° above zero and the freezing point is 32° above zero.

Flammable gas is a Division 2.1 material that is ignitable at 14.7 psi (101.3 kPa) when in a mixture of 13 percent or less by volume, or has a flammable range at 14.7 psi (101.3 kPa) with air of at least 12 percent regardless of the lower limit.

Flammable liquid is a Class 3 material in a liquid form that has a flashpoint of not more than 140° F (60° C), or any material in a liquid phase with a flashpoint at or above 100° F (38° C).

Flammable solid is a Division 4.1 material that includes any solid material (other than one classed as an explosive) that under normal transport and handling conditions is likely to cause fire through friction or retained heat from manufacturing or processing, or that can be ignited readily and, when ignited, can burn vigorously and persistently and create a serious transportation hazard.

Flashpoint means the minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid. The test criteria is cited in 49 CFR 173.120(c).

Gas means a material that has a vapor pressure greater than 43.5 psi (300 kPa) at 122° F (50° C) or is completely gaseous at 68° F (20° C) at a standard pressure of 14.7psi (101.3 kPa). Also, see compressed gas.

Hazard class means the category to which a hazardous material is assigned under the definitions set by DOT in 49 CFR. Even though a material is assigned to only one hazard class, it may meet the defining criteria for more than one hazard class. Some hazardous materials may also have subsidiary hazard class assignment.

Hazard zone refers to one of the four levels of hazards (Hazard Zones A through D) assigned to gases and liquids that are poisonous by inhalation. A hazard zone is based on the LC50 value for acute inhalation and toxicity of gases and vapors. Hazardous materials assigned a hazard zone are nonmailable.

Hazardous material is any article or substance designated by the U.S. Department of Transportation (DOT) as being capable of posing an unreasonable risk to health, safety, or property during transportation. In international commerce, hazardous materials are known as “dangerous goods.”

Hazardous substance is a hazardous material that when shipped in certain quantities can be an environmental hazard. Appendix A in 49 CFR 172.101 lists all hazardous substances. All hazardous substances are hazardous materials, but not all hazardous materials are hazardous substances. Hazardous substances are nonmailable.

Hazardous waste is any material subject to the Hazardous Waste Manifest Requirements of EPA as specified in 40 CFR 262. The only type of hazardous waste permitted in domestic mail is medical waste (i.e., sharps and other medical devices) as specified in 346.

IATA refers to the International Air Transportation Association. IATA annually publishes the IATA Dangerous Goods Regulations, which provides procedures for shippers to prepare hazardous materials for safe transport by air via commercial air transportation. The IATA regulations contain all of the ICAO Technical Instructions as well as some more restrictive requirements that reflect air transport industry standard practices or operational considerations.

ICAO refers to the International Civil Aviation Organization. ICAO biannually publishes the Technical Instructions for the Safe Transport of Dangerous Goods by Air, which specifies the procedures for shipping hazardous materials via air transportation and is recognized by DOT in 49 CFR 171.11.

ID8000 is a miscellaneous hazardous class specific to certain materials within Classes 2, 3, 6.1, and 9 that can qualify as a mailable consumer commodity material and are reclassed as ID8000 when intended for air transportation.

IMO refers to the International Maritime Organization, which provides requirements for shipping hazardous materials via waterways.

Infectious substance (etiologic agent) is a Division 6.2 material that is a viable microorganism, or its toxin, and causes or may cause disease in human beings or animals, and includes those agents listed in 42 CFR 72.3 and any other agent that causes or may cause severe, disabling, or fatal disease. The terms “infectious substance” and “etiologic agent” are synonymous.

Inhalation hazard, see hazard zone.

Inner receptacle, see primary receptacle.

Irritating material is any Division 6.1 liquid or solid substance (e.g., tear gas) that gives off intense fumes and causes extreme but temporary irritation and impairment to a person’s ability to function.

kPa means kilopascals.

L or l means liter.

Limited Quantity is the maximum amount of a specific hazardous material that is exempted from the labeling or packaging requirements in 49 CFR. To be permitted in the Postal Service, hazardous materials that are classified to be shipped as Limited Quantity must also qualify as a consumer commodity material. See Consumer Commodity, Limited Quantity air and Limited Quantity surface.

Limited Quantity Air is a category unique to the Postal Service of a hazardous material in hazard Classes 5, 8, and portions of 9 that presents a limited hazard specifically in air transportation and is mailable under certain conditions in Postal Service air networks.

Limited Quantity Surface is a material that contains a limited quantity of a hazardous material that presents a limited hazard during transportation due to its form, quantity, and packaging, specific to the Postal Service, and is restricted to surface transportation. This category generally must also qualify as a consumer commodity to be accepted in the Postal Service network. This material was previously classified as ORM-D.

Liquid is a material, other than an elevated temperature material, with a melting point of 68° F (20° C) or lower at a standard pressure of 14.7 psi (101.3 kPa).

Liquid phase means a material that meets the definition of a liquid when elevated at the higher of the temperature at which it is offered for transportation, not at the 100° F (38° C) temperature.

Mailable Limited Quantity is a hazardous material in hazard Classes 4, 5, 8 or portions of 9 that presents a limited hazard during transportation (specifically air transport), and is mailable in USPS air networks under certain conditions and in limited quantities.

Magnetized material is an article that has a magnetic field strength capable of causing the deviation of aircraft instruments and producing erroneous aircraft magnetic compass readings.

Marine pollutant is any hazardous material listed in Appendix B of 49 CFR 172.101, including mixtures or solutions of certain concentrations that are capable of polluting water habitats. Marine pollutants are not mailable.

Material Safety Data Sheet (MSDS), see Safety Data Sheet (SDS).

Maximum capacity means the maximum volume permitted in the inner receptacle or packaging.

Miscellaneous hazardous materials are Class 9 substances or articles that present a hazard during transportation but do not meet the definition of any other hazard class. Examples are dry ice and magnetized materials.

ml means milliliter.

mm means millimeters.

NA number refers to the North American (NA) four-digit identification number assigned to a hazardous material that is not recognized for international transportation. Hazardous materials having NA numbers may be shipped in commercial commerce only within the United States or between the United States and Canada. Hazardous materials with NA numbers may be mailed within the United States only as permitted in Chapter 3.

Nonflammable gas is a Division 2.2 material that exerts an absolute pressure of 40.6 psia (280 kPa) or greater at 68° F (20° C).

n.o.s. means not otherwise specified.

Organic peroxide is a Division 5.2 material that includes any organic compound containing oxygen in the bivalent structure and that may be considered a derivative of hydrogen peroxide, where one or more of the hydrogen atoms have been replaced by organic radicals.

ORM means other regulated material.

ORM-D (other regulated materials for domestic transport only) was a marking for mail or shipping in the United States. Packages bearing this mark contained hazardous material in a limited quantity that present a limited hazard during transportation, due to its form, quantity, and packaging. ORM-D was phased out by the U.S. Department of Transportation on Jan. 1, 2021.

OSHA refers to the Occupational Safety and Health Administration of the U.S. Department of Labor. OSHA regulations are codified in Title 29, Code of Federal Regulations (29 CFR).

Other medical devices are Division 6.2 materials that include all articles or devices used in animal or human patient care or treatment or in medical research that are not, or do not contain, a projecting sharp and are not known or not reasonably believed to contain an infectious substance (etiologic agent).

Outer packaging is the outermost enclosure that provides protection against the unintentional release of the contents under normal handling conditions. The outer packaging holds the primary receptacle, the secondary packaging (if required), and the absorbent material and cushioning. The outer packaging bears the addressing information along with all required markings and labels.

Oxidizing gas means a gas that more than air may cause or contribute to the combustion of other material by generally providing oxygen.

Oxidizing substance is a Division 5.2 material that may, generally by yielding oxygen, cause or enhance the combustion of other materials.

Packing group (PG) is the DOT grouping assignment that is based on the degree of danger present in an individual hazardous material. Packing Group I indicates a great danger; Packing Group II, medium danger; Packing Group III, minor danger. Not every hazard class uses packing group assignments. ORM-D materials most often fall within Packing Group III.

Passenger-carrying aircraft means an aircraft that carries any person other than a crew member or company employee, an authorized representative of the United States, or a person accompanying the shipment.

Poisonous gas, see toxic gas.

Poisonous material, see toxic substance.

Primary hazard refers to the single or most dangerous hazard characteristic of a hazardous material (i.e., hazard class or division assignment).

Primary receptacle is the innermost container (i.e., tube, vial, bottle, vessel) that holds the hazardous material. Sometimes the primary receptacle may be referred to as the inner receptacle or the primary container.

Proper shipping name is the name of a hazardous material that must be used to identify a substance or article in the shipping documents and on the packaging, as required. See Appendix A and B for listings of proper shipping names.

psi means pounds per square inch.

psia means pounds per square inch absolute.

psig means pounds per square inch gauge.

Pyrophoric material is a liquid or solid that, even in a small amount and without an external ignition source, can ignite within 5 minutes after coming in contact with air.

Radiation level means the radiation dose-equivalent rate expressed in millisievert per hour (mSv/h) or millirem per hour (mrem/h).

Radioactive instrument or article means any manufactured instrument or article, such as an instrument, clock, electronic tube or apparatus, or similar item, having a Class 7 radioactive material in gaseous or nondispersible solid form as a component part.

Radioactive material is defined in 49 CFR 173.403 as any material containing radionuclides where both the activity concentration and the total activity in the consignment exceed the values specified in the table in 49 CFR 173.436 or values derived according to the instructions in 49 CFR 173.433. Activity limits for mailable Class 7 radioactive materials are listed in
Exhibit 347.22.

Regulated medical waste is the DOT term for a Division 6.2 waste or reusable material, other than a culture or stock of an infectious substance, that may or may not contain an infectious substance and is generated from: the diagnosis, treatment, or immunization of human beings or animals; research pertaining to the diagnosis, treatment, or immunization of human beings or animals; or the production or testing of biological products. Only the types of medical waste named in 346 are mailable.

Reportable quantity (RQ) mean the minimum amount of a hazardous substance that is subject to the additional marking and documentation requirements in Appendix A of 49 CFR 172.101. A hazardous material having an RQ is nonmailable.

Residue means the hazardous material remaining in a packaging after the contents have been unloaded to the maximum extent practicable and before the packaging is either cleaned, refilled, or properly disposed of.

Rigid means unable to bend or be forced out of shape; not flexible. A rigid outer shipping container or rigid packaging is generally interpreted to mean a fiberboard (cardboard) box or outer packaging of equivalent strength, durability and rigidity.

Safety Data Sheet (SDS) is a document that details the physical characteristics and health hazards of a chemical or hazardous product. In 29 CFR 1910.1200(g), OSHA requires chemical manufacturers, distributors, and importers to provide SDSs to communicate the hazards of hazardous chemicals they produce or import, and provide copies to their customers. OSHA also requires that employers have an SDS on hand for each hazardous chemical present in their workplace. For postal purposes, the information on an SDS can be useful in determining the mailability of a hazardous material.

Salvage packaging is a special form of packaging into which damaged, defective, or leaking hazardous materials packages are placed for purposes of recovery or disposal. Salvage packaging must meet the specifications in 49 CFR 173.3.

Secondary packaging container is the packaging component into which the primary receptacle(s) and any required absorbent and cushioning material is securely placed. The packaging of certain mailable hazardous materials requires the use of a secondary container. The secondary packaging container is then secured in an outer shipping container.

Self-heating material is a material that, when in contact with air and without an energy supply, is liable to self-heat and may spontaneously ignite.

Sharps is a Division 6.2 material that includes any item of medical waste having a projecting cutting edge or fine point that was used in animal or human patient care or treatment or in medical research or industrial laboratories. The term includes, but is not limited to, hypodermic needles, syringes (with or without the attached needles), pasteur pipettes, scalpel blades, blood vials, needles with attached tubing, and culture dishes (regardless of the presence of infectious agents). Also included are other types of broken or unbroken glassware that were in contact with infectious agents, such as used slides or cover slips. The term does not include new unused medical devices such as hypodermic needles, syringes, and scalpel blades.

Shipping papers means the shipping order, bill of lading, manifest, or other shipping document that contains the information required by 49 CFR 172.200 through 172.204. Most hazardous materials (including ORM-D materials) sent via air transportation require a shipper’s declaration for dangerous goods. See 326 and Exhibit 326. The Packaging Instructions in Appendix C specify when a shipper’s declaration is required.

Siftproof packaging means a packaging that is impermeable to dry contents, including any fine solid material produced during transportation.

Small quantity is the maximum amount of a specific hazardous material that is not subject to any requirements other than those in 49 CFR 173.4. Not every hazardous material is eligible to be shipped as a small quantity. The small quantity provision is recognized for use within the United States only. A hazardous material cannot be sent in international mail using the small quantity provision.

Solid is a material that is not a liquid or a gas.

Solution is any homogeneous liquid mixture of two or more chemical compounds or elements that will not undergo any segregation under normal transportation conditions.

Specific activity refers to the activity of the radionuclide per unit mass of that nuclide for a Class 7 material.

Specification packaging means a packaging conforming to one of the specifications or standards in 49 CFR 178 and 179. ORM-D materials do not require specification packaging (but they must meet postal packaging requirements).

Spontaneously combustible material is a pyrophoric or a self-heating material that is capable of spontaneous ignition.

Subsidiary hazard means a hazard characteristic, other than the primary hazard, present in a hazardous material that is of lesser significance than the primary hazard.

Surface transportation requirements apply to all mailable hazardous materials sent at the USPS Retail Ground, Parcel Select, or USPS Marketing Mail Parcel prices and must meet the requirements that apply to surface transportation.

TBq means terabecquerel.

Toxic gas is a Division 2.3 material that is poisonous by inhalation and is a gas at 68° F (20° C) or less and a pressure of 14.7 psi (101.3 kPa); or a material that has a boiling point of 68° F (20° C) or less at 14.7 psi (101.3 kPa).

Toxic substance means a material, other than a gas, that is known to be so toxic to humans as to cause death, injury, or harm to health if swallowed, inhaled, or contacted by the skin. See 346 for information on toxicity levels.

UN number refers to the United Nations (UN) four-digit identification number assigned to a hazardous material that is recognized for use in international and domestic commerce and transportation.

UN standard packaging means a packaging that conforms to the standards in the UN Recommendations on the Transport of Dangerous Goods.

Viscosity is the tendency of a fluid to resist internal flow without regard to its density.

Volatility refers to the relative rate of evaporation of materials to assume a vapor state at ordinary temperatures.

Water reactive material, see dangerous when wet material.

Water resistant means having a degree of resistance to permeability and damage caused by water.