343 Flammable and Combustible Liquids
(Hazard Class 3)

343.1 Definition

The terms used in the standards that apply to Hazard Class 3 are defined as follows:

1. Flammable Liquid means a liquid that has a flashpoint of not more than 140° F (60° C), or any material in a liquid phase that has a flashpoint at or above 100° F (38° C).
2. Combustible Liquid means any liquid that does not meet the definition of any other hazard class and has a flashpoint above 140° F (60° C) and below 200° F (93° C). A flammable liquid with a flashpoint at or above 100° F (38° C) that does not meet the definition of any other hazard class may be reclassified as a combustible liquid per 49 CFR 173.120(b).

Note: A liquid with a flashpoint above 200° F (93° C) is not regulated as a hazardous material and may be mailed subject to the general packaging requirements in DMM 601.1-7, provided it possesses no characteristics of another hazard class.

343.2 Mailability and Packaging

343.21 Requirements for Flammable Liquids

The following conditions apply:

1. International Mail. Flammable liquid is prohibited.
2. Domestic Mail via Air Transportation. Flammable liquid is prohibited.
3. Domestic Mail via Surface Transportation. Flammable liquid with a flashpoint of 20° F (–7° C) or below is prohibited. Other flammable liquids are permitted if the material qualifies as a Limited Quantity ground material and meets the criteria in Exhibit 343.21. A mailable flammable liquid must be prepared according to Packaging Instruction 3A in Appendix C, as applicable.

 

Exhibit 343.21 

Flammable Liquids

Flashpoint	Mailability
20° F (–7° C) or below	Not acceptable for mailing.
Above 20° F (–7° C) but not more than 73° F (23° C)	Acceptable (with restrictions) for domestic mail via surface transportation only. Follow requirements for Packaging Instruction 3A in Appendix C, as applicable.
Above 73° F (23° C) but less than 100° F (38° C)	Acceptable (with restrictions) for domestic mail via surface transportation only. Follow requirements for Packaging Instruction 3A in Appendix C, as applicable.
100° F (38° C) and up to 140° F (60° C)	Acceptable (with restrictions) for domestic mail via surface transportation only. Follow requirements for Packaging Instruction 3A or 3B in Appendix C, as applicable. Note: If the flashpoint is between 100° F (38° C) and 140° F (60° C), the liquid may be eligible to be reclassed as a combustible liquid.
Over 140° F (60° C)	See combustible liquids in 343.22. Follow requirements for Packaging Instruction 3B in Appendix C.

343.22 Requirements for Combustible Liquids

The following conditions apply:

1. International Mail. Combustible liquid is prohibited.
2. Domestic Mail via Air Transportation. Combustible liquid is permitted if the material can qualify as an ID8000 material (see 335) and meets the criteria in Exhibit 343.22. Packaging Instruction 3B in Appendix C must be followed, as applicable.
3. Domestic Mail via Surface Transportation. Combustible liquids are permitted if the material qualifies as a Limited Quantity and a consumer commodity material, and meets the criteria in Exhibit 343.22. Packaging Instruction 3B in Appendix C must be followed, as applicable.

 

Exhibit 343.22 

Combustible Liquids

Flashpoint	Mailability
Below 100° F (38° C)	Not a combustible liquid. See flammable liquids in 343.21.
100° F (38° C) but not more than 140° F (60° C)	A flammable liquid that may be eligible to be reclassified as a combustible liquid under 49 CFR 173.120(b). See 343.1. Acceptable (with restrictions) in domestic mail via surface transportation only. Follow requirements for Packaging Instruction 3B in Appendix C, as applicable.
Above 140° F (60° C) but not more than 200° F (93° C)	Acceptable (with restrictions) for domestic mail via air transportation or surface transportation. Follow requirements for Packaging Instruction 3B in Appendix C, as applicable.
Above 200°F (93°C)	The material is not regulated as a hazardous material. Such nonregulated materials must be properly and securely packaged to prevent leakage under the general packaging requirements in DMM 601.3.4.

343.23 Nonmailable Flammable and Combustible Liquids

When flammable liquids and combustible liquids that are nonmailable under 343.21 or 343.22 are found in the mailstream, the procedures in POM 139.117 must be followed if the materials present an immediate threat to persons or property.

The following materials are nonmailable:

1. All flammable liquids having a flashpoint of 20° F (–7° C) or below are prohibited from mailing.
2. Gasoline (UN1203) is a flammable liquid that normally has a flashpoint of –50° F. Gasoline is nonmailable under any circumstances.
3. Acetone (UN1090) normally has a flashpoint of 0° F, Benzene (UN1114) normally has a flashpoint of 12° F, and Hexane(s) (UN1208) normally have flashpoints in the vicinity of -15° F. All are nonmailable unless diluted with less flammable or nonflammable materials sufficient to raise the flashpoint to 20° F or higher.

343.24 Mailable Flammable and Combustible Liquids

The following are mailable:

1. Paint or a related item (UN1263) classified as a flammable or combustible liquid is generally acceptable for mailing provided it can qualify as a Limited Quantity surface material and is sent within the quantity limitations and packaging requirements stated in 343.21 or 343.22, as applicable. Also see 343.26. Mailpieces must be prepared following Packaging Instruction 3A or 3B in Appendix C, as applicable.
2. Latex Paint or a similar water–based paint product that is not flammable or combustible is not regulated as a hazardous material, and therefore is not restricted. Also see 343.26. Mailpieces must be properly packaged under DMM 601.1-7.
3. Canned Heat (Sterno) is a flammable liquid that normally has a flashpoint from 40° F (4° C) to 80° F (27° C). It is permitted if it can qualify as a Limited Quantity surface material and is sent within the quantity limitations and packaging requirements stated in 343.21. Mailpieces must be prepared following Packaging Instruction 3A in Appendix C.
4. Lighter Fluid is a flammable liquid that normally has a flashpoint between 20° F (-7° C) and 55° F (13° C). It is permitted only in domestic mail via surface transportation provided the fluid can qualify as a Limited Quantity surface material and is sent within the quantity limitations and packaging requirements stated in 343.21. Mailpieces must be prepared following Packaging Instruction 3A in Appendix C.
5. Diesel Fuel (NA1993) is a combustible liquid that normally has a flashpoint between 110° F (43° C) and 190° F (88° C). It is acceptable for mailing provided the fluid can qualify as a Limited Quantity surface material, and the liquid is sent within the conditions stated in 343.22. Mailpieces must be prepared following Packaging Instruction 3B in Appendix C.
6. Fuel Oil (NA1993) is a flammable liquid that normally has a flashpoint below 100° F (38° C). The specific flashpoint must be accurately identified by the mailer before a mailability determination can be made. Fuel oil is mailable if it can qualify as a Limited Quantity surface material and is sent within the quantity limitations and packaging requirements stated in 343.21 or 343.22, as applicable. Mailpieces must be prepared following Packaging Instruction 3A or 3B in Appendix C.
7. Adhesives and Cements (UN1133) that are classified as flammable or combustible liquids are mailable only if they can qualify as Limited Quantity surface materials and the applicable conditions in 343.21 or 343.22 are met. Mailpieces must be prepared following Packaging Instruction 3A or 3B in Appendix C, as applicable.

Note: Some adhesives and cements are extremely toxic and may be classified as Division 6.1 toxic substances. Division 6.1 materials are mailable only as permitted in 346.21.

8. Cleaning Agents and Solvents that are classified as flammable liquids are mailable only if they can qualify as Limited Quantity surface materials, and the applicable conditions in 343.21 can be met. Mailpieces must be prepared following Packaging Instruction 3A in Appendix C.

Note: Some cleaning agents and solvents are extremely toxic or corrosive and may be classified as either a Division 6.1 toxic substance or a Class 8 corrosive. Division 6.1 toxic materials and Class 8 corrosives are permitted only within the conditions of 343.21 and 348.2 respectively.

9. Model Fuel (for glow–plug engines) is a flammable liquid that has a flashpoint ranging from 65° F to 75° F. It is mailable only if it can qualify as Limited Quantity surface material, and is sent within the quantity limitations and packaging requirements stated in 343.21. Mailpieces must be prepared following Packaging Instruction 3A in Appendix C.
10. Waxes and Polishes have a wide range of flashpoints. The flashpoint and toxicity must be accurately identified by the mailer before mailability can be determined. Any waxes or polishes that are flammable or combustible liquids are permitted to be mailed, provided they can qualify as a Limited Quantity surface material and the applicable conditions in 343.21 and 343.22 are met. Mailpieces must be prepared following Packaging Instruction 3A or 3B in Appendix C, as applicable.

343.25 Lighters

A lighter equipped with an ignition element and containing liquid fuel is classified as a Class 3 flammable liquid. A lighter containing a flammable gas is classed as a Division 2.1 flammable gas. A lighter that contains either flammable liquid or flammable gas is permitted only in the domestic mail via surface transportation with prior written approval and within these conditions:

1. The design of the lighter is certified by a lighter testing agency authorized by the DOT Associate Administrator for Hazardous Materials Safety, per 49 CFR 173.21(i) and 173.308, and an Approval Number (LAA****) is issued.
2. The prospective mailer of the lighter submits to the PCSC manager a written request for authorization to mail the lighter, accompanied by a legible photocopy of the official DOT notice conveying the approval described in 343.25a, along with a specimen of the actual lighter, the packaging materials in which each lighter is to be mailed, and the number of mailpieces and mailing location; the mailer receives from the PCSC manager a letter approving the requested authorization for mailing.
3. The packaging must be designed to protect the lighter’s sparking mechanism from accidental ignition caused by friction or external pressure during transport. Packaging Instruction 3C in Appendix C must be followed.
4. When presented for mailing, the address side of the mailpiece must prominently display the proper shipping name “Lighter(s)” or “Lighter Refill(s)” followed by the Approval Number (LAA****) and the marking “Surface Only” or “Surface Mail Only,” and all preparation and packaging requirements in the PCSC manager’s approval letter must be met. A legible photocopy of the PCSC manager’s approval must accompany the mailing at the time of deposit.
5. A shipper’s declaration for dangerous goods is not required.

343.26 Paints, Paint–Related Materials, and Inks

The following definitions apply:

1. Paint (UN1263) is the proper shipping name and description for paint, lacquer, enamel, stain, shellac, varnish, liquid aluminum, liquid bronze, liquid gold, liquid wood filler, and liquid lacquer base. Paint–related material (UN1263) is the proper shipping name and description for a paint–thinning, paint–drying, paint–reducing, or paint–removing compound. See 343.24a and 343.24b for mailability.
2. Inks are defined as colored liquids used for writing, drawing, etc., and liquids and pastes used in printing. Printing inks usually are mixtures of finely divided pigments, such as carbon black suspended in a drying oil. Inks classified as combustible or flammable liquids are generally mailable, provided they qualify as Limited Quantity surface material, and meet the applicable requirements in 343.21 or 343.22. Mailpieces must be prepared using Packaging Instruction 3A or 3B in Appendix C, as applicable. The following conditions apply:
1. Regardless of the size or type of container, the primary receptacle(s) containing inks must be cushioned with sufficient absorbent material to take up all liquid contents in case of leakage.
2. The primary receptacle(s) and the absorbent cushioning material must be packed within a sealed, leakproof outer packaging.
3. Inks that are flammable or combustible liquids must meet the quantity restrictions, packaging requirements, and air or surface transportation conditions that apply under 343.2.

Note: Inks that do not possess any hazardous characteristics are not regulated as hazardous materials and are mailable if properly prepared under the standards for packaging liquids in 451.3 and DMM 601.3.4.

343.27 Authorization to Mail Ethanol-Based Flammable Liquids or Solids

Flammable liquids or solids that contain ethyl alcohol are eligible to be mailed via domestic air transportation only with prior written authorization.

Mailers must submit a letter of request to the manager, Product Classification (see 214 for address). The request must include a list of each specific product to be mailed under the authorization, an MSDS for each product, the office of mailing, and expected frequency and quantity of mailings.

Approvals are initially provided for the duration of one year. Subsequent approvals are performance-based and will be extended in one- to three-year increments.

If approved, the mailer must:

1. Present a copy of their authorization letter from the manager, Product Classification (to be kept on file at the office of mailing) at the time of their first mailing at any given Postal Service facility. Mailings not supported by an authorization letter will be refused.
2. For content containing not more than 70% ethyl alcohol by volume, tender only parcels weighing 25 pounds or less. Each non-glass primary receptacle must not exceed 16 ounces of flammable liquid or 1 pound of solids. Each glass primary receptacle must not exceed 8 ounces of flammable liquid or 1/2 pound of solids. Total volume of flammable material per mailpiece must not exceed 96 ounces for flammable liquids or 16 pounds for flammable solids.
3. For content containing more than 70% ethyl alcohol by volume, tender only parcels weighing 16 pounds or less. Each primary package receptacle must not exceed 8 ounces of flammable liquid or 1/2 pound of solids. Total volume of flammable material per mailpiece must not exceed 48 ounces for flammable liquids or 8 pounds for flammable solids.
4. Enter parcels using Priority Mail Express, Priority Mail, First-Class Mail, or First-Class Package Service.
5. Label each parcel on the address side with the mailer’s company name and return address.
6. Label each parcel on the address side with the marking “Contains Air-Eligible Ethyl Alcohol — Authorization Number #,” using at least 14-point type.
7. Ensure that the addressee of each parcel is notified that the addressee is not authorized to re-mail the contents of the parcel via air transportation. The mailer must include the following written notice:

“Flammable liquids or solids contained in these packages may be mailed only by consumers (the addressee) via surface transportation in accordance with USPS Publication 52, section 343. Full responsibility rests with the mailer to comply with all postal and nonpostal statutes and regulations regarding mail. Information regarding postal statutes, regulations, and mailing requirements is available from your local Postmaster or district manager, Business Mail Entry, and at the Postal Service’s mailing standards website, Postal Explorer, at pe.usps.com.”

8. Comply with the warning and labeling requirements set forth in 21 CFR 700, 701.3, and 740.1 when mailing each parcel.
9. Comply with all quantity, packaging, and marking requirements in Packaging Instruction 3D in Appendix C.

343.3 Marking and Documentation

All labels and text markings must be placed on the address side of the mailpiece unless specified in 221.1 and 325.1. Parcels containing mailable flammable or combustible liquids must be marked as follows:

1. For air transportation, parcels containing mailable Class 3 materials must bear the DOT square-on-point marking. The top and bottom portions of the square-on-point and the border forming the square-on-point must be black, and the center must be white or of a suitable contrasting background. The symbol “Y” must be black, located in the center of the square-on-point, and clearly visible. Mailpieces must also be marked with the proper shipping name “Consumer Commodity” and identification number “ID8000.” Each mailpiece must also bear an approved DOT Class 9 hazardous material warning label (see
   Exhibit 325.3b). A properly completed shipper’s declaration for dangerous goods prepared in triplicate must be affixed to the outside of the mailpiece.
2. For surface transportation, parcels containing mailable Class 3 materials must be plainly and durably marked on the address side with an approved DOT Limited Quantity marking (see Exhibit 325.4). Surface shipments bearing Limited Quantity ground markings are not required to include the proper shipping name and identification number. A shipper’s declaration for dangerous goods is not required for mailable Class 3 materials sent via surface transportation.
3. Markings must be durable, legible, and readily visible, and must be applied on at least one side or one end of the outer packaging. The border forming the square-on-point must be at least 2 mm in width, and the minimum dimension of each side must be 100 mm, unless the package size requires a reduced size marking of no less than 50 mm on each side.
4. Lighters containing flammable liquids or gases must be marked as specified in 343.25.
5. Ethanol-based flammable liquids or solids must be marked as specified in 343.27 and Appendix C, Packaging Instruction 3D.