###### Editorial Note on [Part 173](/current/title-49/part-173?toc=1)

#### Editorial Note:

Nomenclature changes to part 173 appear at [70 FR 56098](https://www.federalregister.gov/citation/70-FR-56098), Sept. 23, 2005.

#### § 173.2a Classification of a material having more than one hazard.

(a) *Classification of a material having more than one hazard.* Except as provided in [paragraph (c)](/on/2024-09-24/title-49/section-173.2a#p-173.2a(c)) of this section, a material not specifically listed in the [§ 172.101](/on/2024-09-24/title-49/section-172.101) Table or assigned to an entry of articles containing hazardous materials (UN3537 to UN3548) that meets the definition of more than one hazard class or division as defined in this part, shall be classed according to the highest applicable hazard class of the following hazard classes, which are listed in descending order of hazard:

(1) Class 7 (radioactive materials, other than limited quantities; and shipments of UN 3507, Uranium hexafluoride, radioactive material, excepted package)

(2) Division 2.3 (poisonous gases).

(3) Division 2.1 (flammable gases).

(4) Division 2.2 (nonflammable gases).

(5) Division 6.1 (poisonous liquids), Packing Group I, poisonous-by-inhalation only.

(6) A material that meets the definition of a pyrophoric material in [§ 173.124(b)(1) of this subchapter](/on/2024-09-24/title-49/section-173.124#p-173.124(b)(1)) (Division 4.2).

(7) A material that meets the definition of a self-reactive material in [§ 173.124(a)(2) of this subchapter](/on/2024-09-24/title-49/section-173.124#p-173.124(a)(2)) (Division 4.1).

(8) Class 3 (flammable liquids), Class 8 (corrosive materials), Division 4.1 (flammable solids), Division 4.2 (spontaneously combustible materials), Division 4.3 (dangerous when wet materials), Division 5.1 (oxidizers) or Division 6.1 (poisonous liquids or solids other than Packing Group I, poisonous-by-inhalation). The hazard class and packing group for a material meeting more than one of these hazards shall be determined using the precedence table in [paragraph (b)](/on/2024-09-24/title-49/section-173.2a#p-173.2a(b)) of this section.

(9) Combustible liquids.

(10) Class 9 (miscellaneous hazardous materials).

(b) *Precedence of hazard table for Classes 3 and 8 and Divisions 4.1, 4.2, 4.3, 5.1 and 6.1.* The following table ranks those materials that meet the definition of Classes 3 and 8 and Divisions 4.1, 4.2, 4.3, 5.1 and 6.1:

Precedence of Hazard Table

[ Hazard class or division and packing group ]

| | 4.2 | 4.3 | 5.1 I1 | 5.1 II1 | 5.1 III1 | 6.1, I dermal | 6.1, I oral | 6.1 II | 6.1 III | 8, I liquid | 8, I solid | 8, II liquid | 8, II solid | 8, III liquid | 8, III solid |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 3 I2 | | 4.3 | | | | 3 | 3 | 3 | 3 | 3 | (3) | 3 | (3) | 3 | (3) |
| 3 II2 | | 4.3 | | | | 3 | 3 | 3 | 3 | 8 | (3) | 3 | (3) | 3 | (3) |
| 3 III2 | | 4.3 | | | | 6.1 | 6.1 | 6.1 | 34 | 8 | (3) | 8 | (3) | 3 | (3) |
| 4.1 II2 | 4.2 | 4.3 | 5.1 | 4.1 | 4.1 | 6.1 | 6.1 | 4.1 | 4.1 | (3) | 8 | (3) | 4.1 | (3) | 4.1 |
| 4.1 III2 | 4.2 | 4.3 | 5.1 | 4.1 | 4.1 | 6.1 | 6.1 | 6.1 | 4.1 | (3) | 8 | (3) | 8 | (3) | 4.1 |
| 4.2 II | | 4.3 | 5.1 | 4.2 | 4.2 | 6.1 | 6.1 | 4.2 | 4.2 | 8 | 8 | 4.2 | 4.2 | 4.2 | 4.2 |
| 4.2 III | | 4.3 | 5.1 | 5.1 | 4.2 | 6.1 | 6.1 | 6.1 | 4.2 | 8 | 8 | 8 | 8 | 4.2 | 4.2 |
| 4.3 I | | | 5.1 | 4.3 | 4.3 | 6.1 | 4.3 | 4.3 | 4.3 | 4.3 | 4.3 | 4.3 | 4.3 | 4.3 | 4.3 |
| 4.3 II | | | 5.1 | 4.3 | 4.3 | 6.1 | 4.3 | 4.3 | 4.3 | 8 | 8 | 4.3 | 4.3 | 4.3 | 4.3 |
| 4.3 III | | | 5.1 | 5.1 | 4.3 | 6.1 | 6.1 | 6.1 | 4.3 | 8 | 8 | 8 | 8 | 4.3 | 4.3 |
| 5.1 I1 | | | | | | 5.1 | 5.1 | 5.1 | 5.1 | 5.1 | 5.1 | 5.1 | 5.1 | 5.1 | 5.1 |
| 5.1 II1 | | | | | | 6.1 | 5.1 | 5.1 | 5.1 | 8 | 8 | 5.1 | 5.1 | 5.1 | 5.1 |
| 5.1 III1 | | | | | | 6.1 | 6.1 | 6.1 | 5.1 | 8 | 8 | 8 | 8 | 5.1 | 5.1 |
| 6.1 I, Dermal | | | | | | | | | | 8 | 6.1 | 6.1 | 6.1 | 6.1 | 6.1 |
| 6.1 I, Oral | | | | | | | | | | 8 | 6.1 | 6.1 | 6.1 | 6.1 | 6.1 |
| 6.1 II, Inhalation | | | | | | | | | | 8 | 6.1 | 6.1 | 6.1 | 6.1 | 6.1 |
| 6.1 II, Dermal | | | | | | | | | | 8 | 6.1 | 8 | 6.1 | 6.1 | 6.1 |
| 6.1 II, Oral | | | | | | | | | | 8 | 8 | 8 | 6.1 | 6.1 | 6.1 |
| 6.1 III | | | | | | | | | | 8 | 8 | 8 | 8 | 8 | 8 |
| | | | | | | | | | | | | | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 See [§ 173.127](/on/2024-09-24/title-49/section-173.127). | | | | | | | | | | | | | | | |
| 2 Materials of Division 4.1 other than self-reactive substances and solid desensitized explosives, and materials of Class 3 other than liquid desensitized explosives. | | | | | | | | | | | | | | | |
| 3 Denotes an impossible combination. | | | | | | | | | | | | | | | |
| 4 For pesticides only, where a material has the hazards of Class 3, Packing Group III, and Division 6.1, Packing Group III, the primary hazard is Division 6.1, Packing Group III. | | | | | | | | | | | | | | | |

Note 1:

The most stringent packing group assigned to a hazard of the material takes precedence over other packing groups; for example, a material meeting Class 3 PG II and Division 6.1 PG I (oral toxicity) is classified as Class 3 PG I.

Note 2:

A material which meets the definition of Class 8 and has an inhalation toxicity by dusts and mists which meets criteria for Packing Group I specified in [§ 173.133(a)(1)](/on/2024-09-24/title-49/section-173.133#p-173.133(a)(1)) must be classed as Division 6.1 if the oral or dermal toxicity meets criteria for Packing Group I or II. If the oral or dermal toxicity meets criteria for Packing Group III or less, the material must be classed as Class 8.

(c) The following materials are not subject to the provisions of [paragraph (a)](/on/2024-09-24/title-49/section-173.2a#p-173.2a(a)) of this section because of their unique properties:

(1) A Class 1 (explosive) material that meets any other hazard class or division as defined in this part shall be assigned a division in Class 1. Class 1 materials shall be classed and approved in accordance with [§ 173.56 of this part](/on/2024-09-24/title-49/part-173/section-173.56);

(2) A Division 5.2 (organic peroxide) material that meets the definition of any other hazard class or division as defined in this part, shall be classed as Division 5.2;

(3) A Division 6.2 (infectious substance) material that also meets the definition of another hazard class or division, other than Class 7, or that also is a limited quantity Class 7 material, shall be classed as Division 6.2;

(4) A material that meets the definition of a wetted explosive in [§ 173.124(a)(1) of this subchapter](/on/2024-09-24/title-49/section-173.124#p-173.124(a)(1)) (Division 4.1). Wetted explosives are either specifically listed in the [§ 172.101](/on/2024-09-24/title-49/section-172.101) table or are approved by the Associate Administrator (see [§ 173.124(a)(1) of this subchapter](/on/2024-09-24/title-49/section-173.124#p-173.124(a)(1))); and

(5) A limited quantity of a Class 7 (radioactive) material that meets the definition for more than one hazard class or division shall be classed in accordance with [§ 173.423](/on/2024-09-24/title-49/section-173.423).

[Amdt. 173-224, [55 FR 52606](https://www.federalregister.gov/citation/55-FR-52606), Dec. 21, 1990, as amended at [56 FR 66264](https://www.federalregister.gov/citation/56-FR-66264), Dec. 20, 1991; Amdt. 173-241, [59 FR 67490](https://www.federalregister.gov/citation/59-FR-67490), Dec. 29, 1994; Amdt. 173-247, [60 FR 48787](https://www.federalregister.gov/citation/60-FR-48787), Sept. 20, 1995; Amdt. 173-244, [60 FR 50307](https://www.federalregister.gov/citation/60-FR-50307), Sept. 28, 1995; [64 FR 10776](https://www.federalregister.gov/citation/64-FR-10776), Mar. 5, 1999; [66 FR 33426](https://www.federalregister.gov/citation/66-FR-33426), June 21, 2001; [66 FR 45182](https://www.federalregister.gov/citation/66-FR-45182), [45379](https://www.federalregister.gov/citation/66-FR-45379), Aug. 28, 2001; [68 FR 45032](https://www.federalregister.gov/citation/68-FR-45032), July 31, 2003; [80 FR 1151](https://www.federalregister.gov/citation/80-FR-1151), Jan. 8, 2015; [85 FR 27878](https://www.federalregister.gov/citation/85-FR-27878), May 11, 2020]