An explosive is any substance or article, including a device, that is designed to function by explosion (an extremely rapid release of gas and heat) or that, by chemical reaction within itself, is able to function in a similar manner even if not designed to function by explosion, unless the substance or article is otherwise classed under the provisions in 49 CFR.
Hazard Class 1 has six divisions as follows:
- Division 1.1 consists of explosives that have a mass explosion hazard. Examples are black powder, nitroglycerine (desensitized), dynamite, most types of torpedoes, and mercury fulminate.
- Division 1.2 consists of explosives that have a projection hazard but not a mass explosion hazard. Examples are certain types of fireworks, some types of detonating fuses, and some types of ammunition.
- Division 1.3 consists of explosives that have a fire hazard and either a minor blast or minor projection hazard or both, but not a mass explosion hazard. Examples are sodium picramate, some liquid and solid propellants, and some rocket motors.
- Division 1.4 consists of explosives that present a minor blast hazard. Examples are common fireworks, toy caps, empty primed grenades, and some small arms ammunition.
- Division 1.5 consists of very insensitive explosives that have a mass explosion hazard. Examples are type E blasting agents, some type B blasting agents, and very insensitive explosive substances.
- Division 1.6 consists of extremely insensitive articles that do not have a mass explosion hazard.
Each division in Class 1 is further assigned a compatibility group code. The compatibility code consists of one letter (A–H, J–L, N, or S) that is positioned after the division number (e.g., 1.1A, 1.2C, 1.4S) and refers to the transportation and storage controls necessary to prevent potential hazards. See 49 CFR 173.52 for a more detailed description of the Class 1 compatibility codes.
Explosives are generally prohibited from mailing under 18 U.S.C. 1716. The following conditions apply to the mailing of explosives:
- International Mail. All explosives are prohibited.
- Domestic Mail via Air Transportation. All explosives are prohibited.
- Domestic Mail via Surface Transportation. Generally, explosives are prohibited. The only exceptions are for Division 1.4S toy propellant devices and safety fuses that have been approved by the Manager, Mailing Standards, USPS Headquarters, Washington, DC prior to mailing as stated in 341.22 and DMM 601.10.11.2.
Nonmailable explosives found in the mailstream must be immediately reported in accordance with POM 139.117.
Nonmailable explosives include, but are not limited to, the following:
- Common Fireworks. Fireworks are classified as Division 1.1, 1.2, 1.3, or 1.4 explosives depending on the degree of hazard. Fireworks include roman candles, skyrockets, helicopter–type rockets, cylindrical and cone fountains, pyrotechnic wheels, illuminating torches, firecrackers, salutes, and combinations of items that are designed to produce any of the aforementioned types of effects. All types of fireworks are prohibited from mailing.
- Fuses. Fuses are classified as Division 1.3 or 1.4 explosives depending on the degree of hazard. All types of fuses (except safety fuses as permitted under 341.22) are prohibited from mailing.
- Small Arms Ammunition. Ammunition is classified as a Division 1.1, 1.2, 1.3, or 1.4 explosive, depending on the degree of hazard. Ammunition that is regulated as a Class 1 explosive and designed to be fired from a pistol, revolver, rifle, or shotgun, as well as associated primers and blank cartridges (including those designed for tools) and propellant powder for use in any firearm, is prohibited from mailing.
The following specific types of explosives may be mailed only when the applicable conditions are met. Full responsibility rests with the mailer to comply with Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) regulations before mailing.
- Toy Propellant Devices. The proper shipping name for a toy propellant device is “model rocket motor” or “igniters.” A toy propellant device assigned UN0454 or NA0323 and classed as a Division 1.4S explosive is eligible for mailing in domestic mail via surface transportation only when prior written permission has been obtained from the Manager, Mailing Standards, USPS Headquarters, Washington, DC. A device approved for mailing is subject to the following conditions:
- Each device must be ignitable by electrical means only; contain no more than 30 g (1.07 oz) of propellant; and produce less than 80 newton seconds of total impulse with thrust duration not less than 0.050 second.
- Each device must be constructed so that all chemical ingredients are preloaded into a cylindrical paper or similarly constructed nonmetallic tube that does not fragment into sharp, hard pieces; must be designed so that it will not burst under normal conditions of use; must be incapable of spontaneous ignition under 500° F; and must not contain any type of explosive or pyrotechnic warhead other than a small, activation–charge, parachute–recovery system.
- Each mailpiece containing approved devices must be prepared for mailing following Packaging Instruction 1A in Appendix C. A shipper’s declaration for dangerous goods is required.
- Safety Fuses (UN0105). Safety fuses consist of a core of black powder over–spun with yarns, waterproofing compounds, and/or tapes. Safety fuses assigned UN0105 as a Division 1.4S explosive may be mailed in domestic mail via surface transportation only when prior written approval has been granted by the Manager, Mailing Standards, USPS Headquarters, Washington, DC. Mailable safety fuses must be prepared using Packaging Instruction 1B in Appendix C. A shipper’s declaration for dangerous goods is required.
Note: “Safety Fuses” are not to be confused with “fusees.” Fusees are rail and highway distress signals that are nonmailable Class 4 flammable solids.
- Shotgun Hulls, Empty Casings, Nonmetallic Shotgun Hulls, or Casings Without Primers. These articles are not classified as explosives or hazardous materials under 49 CFR and, therefore, are mailable subject to the applicable mailing rules (see 227).