344 Flammable Solids (Hazard Class 4)

344.1 Definition

Hazard Class 4 consists of three divisions:

1. Division 4.1, Flammable Solids: Solid materials (other than explosives) that, under typical transport conditions, may ignite through friction or retained heat from manufacturing or processing, or that ignite easily and burn vigorously enough to pose a significant transportation hazard.
2. Division 4.2, Spontaneously Combustible: Liquid or solid pyrophoric materials that can ignite within 5 minutes air exposure without an external ignition source, or self-heating materials that may begin to heat spontaneously when in contact with air, even without an energy supply.
3. Division 4.3, Dangerous When Wet: Materials that, upon contact with water, may become spontaneously flammable or emit flammable or toxic gas at a rate greater than 1 liter per kilogram of the material per hour.

Examples of flammable solids include certain metallic hydrides, metallic sodium and potassium, oily fabrics, processed metals, matches, and nitrocellulose products.

344.2 Mailability

The following conditions apply for mailing Hazard Class 4 items:

1. International Mail: All flammable solids are prohibited.
2. Domestic Mail via Air Transportation: All flammable solids are prohibited.
3. Domestic Mail via Surface Transportation: Flammable solids that qualify as Limited Quantity surface materials are permitted.

344.21 Mailable Flammable Solids

The following flammable solids are permitted for mailing under specified conditions:

1. Limited Quantity Surface Materials: Flammable solids that qualify as Limited Quantity surface materials are permitted in the domestic mail via surface transportation.
2. Safety matches: Book, card, or strike-on-box safety matches are permitted only in domestic mail via surface transportation.

344.3 Packaging, Marking, and Documentation

Labels and text markings must appear on the address side of the mailpiece unless otherwise specified in 221.1 and 325.1. The following conditions apply:

1. Mailable Flammable Solids: Packaging must follow the conditions in Packaging Instruction 4A in Appendix C. Mailpieces containing mailable Class 4 materials must be plainly and durably marked on the address side with an approved DOT Limited Quantity ground marking (refer to 325.4). Shipments bearing the Limited Quantity surface marking do not require the proper shipping name and identification number. A shipping paper is not required for mailable Class 4 materials sent via surface transportation.
2. Safety Matches: Packaging must follow conditions in Packaging Instruction 4B in Appendix C Mailpieces must be plainly and durably marked on the address side with "Surface Only" or "Surface Mail Only" and, as applicable, "Book Matches," "Strike-on-Card Matches," or "Card Matches." A shipping paper is not required.

344.4 Nonmailable Flammable Solids

Nonmailable flammable solids that are found in the mailstream and pose an immediate threat to persons or property must be handled in accordance with the procedures in POM 139.117.

Strike-anywhere matches and safety matches are examples of flammable solids. All flammable solids are prohibited in domestic air transportation and in international mail. Safety matches (book, card, or strike-on-box) are mailable only domestic surface transportation.