---
kind: "section"
citation: "49 C.F.R. § 173.127"
title: "49"
number: "173.127"
heading: "Class 5, Division 5.1—Definition and assignment of packing groups."
url: "https://uscodex.org/cfr/49/173.127"
---

# §173.127. Class 5, Division 5.1—Definition and assignment of packing groups.

- (a) **Definition.** For the purpose of this subchapter, oxidizer (Division 5.1) means a material that may, generally by yielding oxygen, cause or enhance the combustion of other materials.
  - (1) A solid material, except for solid ammonium nitrate based fertilizer (see [paragraph (a)(3)](#a-3) of this section), is classed as a Division 5.1 material if, when tested in accordance with the UN Manual of Tests and Criteria (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter):
    - (i) If test O.1 is used (UN Manual of Tests and Criteria, sub-[section 34.4.1](/cfr/49/34.4.1.md)), the mean burning time is less than or equal to the burning time of a 3:7 potassium bromate/cellulose mixture; or
    - (ii) If test O.3 is used (UN Manual of Tests and Criteria, sub-[section 34.4.3](/cfr/49/34.4.3.md)), the mean burning rate is greater than or equal to the burning rate of a 1:2 calcium peroxide/cellulose mixture.
  - (2) A liquid material is classed as a Division 5.1 material if, when tested in accordance with the UN Manual of Tests and Criteria, it spontaneously ignites or its mean time for a pressure rise from 690 kPa to 2070 kPa gauge is less then the time of a 1:1 nitric acid (65 percent)/cellulose mixture.
  - (3) Solid ammonium nitrate-based fertilizers must be classified in accordance with the procedure as set out in the UN Manual of Tests and Criteria, Part III, [Section 39](/cfr/49/39.md).
- (b) **Assignment of packing groups.**
  - (1) The packing group of a Division 5.1 material which is a solid shall be assigned using the following criteria:
    - (i) **Packing Group I, for any material which, in either concentration tested—**
      - (A) If test O.1 is used (UN Manual of Tests and Criteria, sub-[section 34.4.1](/cfr/49/34.4.1.md)), the mean burning time is less than the mean burning time of a 3:2 potassium bromate/cellulose mixture; or
      - (B) If test O.3 is used (UN Manual of Tests and Criteria, sub-[section 34.4.3](/cfr/49/34.4.3.md)), the mean burning rate is greater than the mean burning rate of a 3:1 calcium peroxide/cellulose mixture.
    - (ii) **Packing Group II, for any material which, in either concentration tested—**
      - (A) If test O.1 is used (UN Manual of Tests and Criteria, sub-[section 34.4.1](/cfr/49/34.4.1.md)), the mean burning time is less than the mean burning time of a 2:3 potassium bromate/cellulose mixture and the criteria for Packing Group I are not met; or
      - (B) If test O.3 is used (UN Manual of Tests and Criteria, sub-[section 34.4.3](/cfr/49/34.4.3.md)), the mean burning rate is greater than the mean burning rate of a 1:1 calcium peroxide/cellulose mixture and the criteria for Packing Group I are not met.
    - (iii) **Packing Group III for any material which, in either concentration tested—**
      - (A) If test O.1 is used (UN Manual of Tests and Criteria, sub-[section 34.4.1](/cfr/49/34.4.1.md)), the mean burning time is less than the mean burning time of a 3:7 potassium bromate/cellulose mixture and the criteria for Packing Groups I and II are not met; or
      - (B) If test O.3 is used (UN Manual of Tests and Criteria, sub-[section 34.4.3](/cfr/49/34.4.3.md)), the mean burning rate is greater than the mean burning rate of a 1:2 calcium peroxide/cellulose mixture and the criteria for Packing Groups I and II are not met.
    - (iv) The materials is not classified as a Division 5.1 material if, in either concentration tested:
      - (A) If test O.1 is used (UN Manual of Tests and Criteria, sub-[section 34.4.1](/cfr/49/34.4.1.md)), the sample tested does not ignite and exhibit burn, or exhibits a mean burning time of greater than or equal to the mean burning time of a 3:7 potassium bromate/cellulose mixture.
      - (B) If test O.3 is used (UN Manual of Tests and Criteria, sub-[section 34.4.3](/cfr/49/34.4.3.md)), the sample tested does not ignite and exhibit burn, or exhibits a mean burning rate less than or equal to the mean burning rate of a 1:2 calcium peroxide/cellulose mixture.
  - (2) The packing group of a Division 5.1 material which is a liquid shall be assigned using the following criteria:
    - (i) **Packing Group I for—**
      - (A) **Any material which spontaneously ignites when mixed with cellulose in a 1—** 1 ratio; or
      - (B) **Any material which exhibits a mean pressure rise time less than the pressure rise time of a 1—** 1 perchloric acid (50 percent)/cellulose mixture.
    - (ii) Packing Group II, any material which exhibits a mean pressure rise time less than or equal to the pressure rise time of a 1:1 aqueous sodium chlorate solution (40 percent)/cellulose mixture and the criteria for Packing Group I are not met.
    - (iii) Packing Group III, any material which exhibits a mean pressure rise time less than or equal to the pressure rise time of a 1:1 nitric acid (65 percent)/cellulose mixture and the criteria for Packing Group I and II are not met.

## Notes

### Amendments

[Amdt. 173-261, 62 FR 24732, May 6, 1997, as amended at 68 FR 75744, Dec. 31, 2003; 80 FR 1156, Jan. 8, 2015; 80 FR 72924, Nov. 23, 2015; 85 FR 27880, May 11, 2020]

### Source

Source: Amdt. 173-224, 55 FR 52634 Dec. 21, 1990, unless otherwise noted.

### Authority

Authority: 49 U.S.C. 5101-5128, 44701; 49 CFR 1.81, 1.96 and 1.97.

### Amendments

[Amdt. 173-261, 62 FR 24732, May 6, 1997, as amended at 68 FR 75744, Dec. 31, 2003; 80 FR 1156, Jan. 8, 2015; 80 FR 72924, Nov. 23, 2015; 85 FR 27880, May 11, 2020]