(a) General. (1) The requirements of this section apply to all cargo spaces on deck or under deck of all types of vessels, and to all cargo transport units.

(2) Segregation is obtained by maintaining certain distances between incompatible hazardous materials or by requiring the presence of one or more steel bulkheads or decks between them or a combination thereof. Intervening spaces between such hazardous materials may be filled with other cargo which is not incompatible with the hazardous materials.

(3) The general requirements for segregation between the various classes of dangerous goods are shown in the segregation table. In addition to these general requirements, there may be a need to segregate a particular material from other materials which would contribute to its hazard. Such segregation requirements are indicated by code numbers in Column 10B of the § 172.101 Table.

(4) Segregation is not required:

(i) Between hazardous materials of different classes which comprise the same substance but vary only in their water content (for example, sodium sulfide in Division 4.2 or Class 8) or quantity for Class 7 materials; or

(ii) Between hazardous materials of different classes which comprise a group of substances that do not react dangerously with each other. The following materials are grouped by compatibility:

(A) Hydrogen peroxide, aqueous solutions with not less than 8 percent but less than 20 percent hydrogen peroxide (stabilized as necessary); Hydrogen peroxide, aqueous solutions with not less than 20 percent but not more than 40 percent hydrogen peroxide; Hydrogen peroxide, aqueous solutions with more than 40 percent but not more than 60 percent hydrogen peroxide; Hydrogen peroxide and peroxyacetic acid mixtures, stabilized with acids, water and not more than 5 percent peroxyacetic acid; Organic peroxide type D, liquid; Organic peroxide type E, liquid; Organic peroxide type F, liquid;

(B) Dichlorosilane, Silicon tetrachloride, and Trichlorosilane; and

(C) Organometallic substance, solid, pyrophoric; Organometallic substance, liquid, pyrophoric; Organometallic substance, solid, pyrophoric, water-reactive; Organometallic substance, liquid, pyrophoric, water-reactive; Organometallic substance, solid, water-reactive; Organometallic substance, solid, water-reactive, flammable; Organometallic substance, solid, water-reactive, self-heating; Organometallic substance, liquid, water-reactive; Organometallic substance, liquid, water-reactive, flammable; and Organometallic substance, solid, self-heating.

(5) Whenever hazardous materials are stowed together, whether or not in a cargo transport unit, the segregation of such hazardous materials from others must always be in accordance with the most restrictive requirements for any of the hazardous materials concerned.

(6) When the § 172.101 Table or § 172.402 requires packages to bear a subsidiary hazard label or labels, the segregation appropriate to the subsidiary hazards must be applied when that segregation is more restrictive than that required by the primary hazard. For the purposes of this paragraph, the segregation requirements corresponding to an explosive subsidiary hazard are—except for organic peroxides which are those corresponding to Division 1.3—those for Division 1.4 (explosive) materials.

(7) Where, for the purposes of segregation, terms such as “away from” a particular hazard class are used in the § 172.101 Table, the segregation requirement applies to:

(i) All hazardous materials within the hazard class; and

(ii) All hazardous materials for which a secondary hazard label of that class is required.

(8) Notwithstanding the requirements of paragraphs (a)(6) and (a)(7) of this section, hazardous materials of the same class may be stowed together without regard to segregation required by secondary hazards (subsidiary risk label(s)), provided the substances do not react dangerously with each other and cause:

(i) Combustion and/or evolution of considerable heat;

(ii) Evolution of flammable, toxic or asphyxiant gases;

(iii) The formation of corrosive substances; or

(iv) The formation of unstable substances.

(9) Stowage in a shelter-'tween deck cargo space is not considered to be “on deck” stowage.

(10) Where the code in column (10B) of the § 172.101 Table specifies that “Segregation as for. . .” applies, the segregation requirements applicable to that class in the § 176.83(b) General Segregation Table must be applied. However, for the purposes of paragraph (a)(8) of this section, which permits substances of the same class to be stowed together provided they do not react dangerously with each other, the segregation requirements of the class as represented by the primary hazard class in the § 172.101 Table entry must be applied.

(11) Certain exceptions from segregation for waste cyanides or waste cyanide mixtures or solutions transported with acids; waste Division 4.2 materials transported with Class 8 liquids; and waste Division 6.1 Packing Group I, Hazard Zone A material transported with waste Class 3 material, Class 8 liquids, and Division 4.1, 4.2, 4.3, 5.1 or 5.2 material are set forth in § 173.12(e) of this subchapter.

(b) General Segregation Table. The following table sets forth the general requirements for segregation between the various classes (divisions) of hazardous materials. Certain divisions are listed as separate hazard classes for the purpose of this table (e.g., “2.1” and “2.2”). The properties of materials within each class may vary greatly and may require greater segregation than is reflected in this table. If the § 172.101 Table sets forth particular requirements for segregation, they take precedence over these general requirements.

(c) Segregation requirements for breakbulk cargo. (1) The requirements of this paragraph apply to the segregation of packages containing hazardous materials and stowed as breakbulk cargo;

(2) Definition of the segregation terms:

(i) Legend:

(A) Package containing incompatible goods.

(B) Reference package.

(C) Deck resistant to fire and liquid.

(ii) “Away from”: Effectively segregated so that the incompatible materials cannot interact dangerously in the event of an accident but may be carried in the same compartment or hold or on deck provided a minimum horizontal separation of 3 m (10 feet) projected vertically is obtained.

(iii) “Separated From”: In different compartments or holds when stowed under deck. If the intervening deck is resistant to fire and liquid, a vertical separation (i.e., in different compartments) is acceptable as equivalent to this segregation. For “on deck” stowage, this segregation means a separation by a distance of at least 6 m (20 feet) horizontally.

(iv) “Separated by a complete compartment or hold from”: Either a vertical or horizontal separation. If the intervening decks are not resistant to fire and liquid, then only a longitudinal separation (i.e., by an intervening complete compartment or hold) is acceptable. For “on deck” stowage, this segregation means a separation by a distance of at least 12 m (39 feet) horizontally. The same distance must be applied if one package is stowed “on deck”, and the other one in an upper compartment.

(v) “Separated longitudinally by an intervening complete compartment or hold from”: Vertical separation alone does not meet this requirement. Between a package “under deck” and one “on deck” a minimum distance of 24 m (79 feet) including a complete compartment must be maintained longitudinally. For “on deck” stowage, this segregation means a separation by a distance of at least 24 m (79 feet) longitudinally.

(d) Segregation in cargo transport units: Two hazardous materials for which any segregation is required may not be stowed in the same cargo transport unit.

(e) Segregation of hazardous materials stowed as breakbulk cargo from those packed in cargo transport units: (1) Hazardous materials stowed as breakbulk cargo must be segregated from materials packed in open cargo transport units in accordance with paragraph (c) of this section.

(2) Hazardous materials stowed as breakbulk cargo must be segregated from materials packed in closed cargo transport units in accordance with paragraph (c) of this section, except that:

(i) Where “away from” is required, no segregation between packages and the closed cargo transport units is required; and

(ii) Where “separated from” is required, the segregation between the packages and the closed cargo transport units may be the same as for “away from”.

(f) Segregation of cargo transport units on board container vessels: (1) Except for hatchless container ships, this paragraph applies to segregation of cargo transport units that are carried on board container vessels, or on other types of vessels, provided these cargo spaces are properly fitted for permanent stowage of containers during transport.

(2) For container vessels which have cargo spaces used for breakbulk cargo or any other method of stowage, the appropriate paragraph of this section applies to the relevant cargo space.

(3) Segregation Table. Table § 176.83(f) sets forth the general requirements for segregation between cargo transport units on board container vessels.

(4) In table § 176.83(f), a container space means a distance of not less than 6 m (20 feet) fore and aft or not less than 2.5 m (8 feet) athwartship.

(g) Segregation of cargo transport units on board trailerships and trainships: (1) The requirements of this paragraph apply to the segregation of cargo transport units which are carried on board trailerships and trainships or in “roll-on/roll-off” cargo spaces.

(2) For trailerships and trainships which have spaces suitable for breakbulk cargo, containers, or any other method of stowage, the appropriate paragraph of this section applies to the relevant cargo space.

(3) Segregation Table. Table § 176.83(g) sets forth the general requirements for segregation between transport units on board trailerships and trainships.

(h) Segregation on board barge carrying vessels: (1) The requirements of this section apply to the segregation in shipborne barges as well as to the segregation between shipborne barges carried on board vessels specially designed and equipped to carry such barges.

(2) On barge-carrying vessels which incorporate other stowage spaces or any other method of stowage, barges containing hazardous materials must be segregated from hazardous materials not stowed in barges as prescribed in paragraphs (b) and (j) of this section.

(i) Segregation in shipborne barges: Hazardous materials transported in shipborne barges must be segregated as prescribed in paragraphs (a), (b), and (c) of this section.

(j) Segregation between shipborne barges on barge-carrying vessels: (1) When a shipborne barge is loaded with two or more hazardous materials with different requirements for segregation, the most stringent applicable segregation requirement must be applied.

(2) “Away from” and “separated from” require no segregation between shipborne barges.

(3) For barge-carrying vessels with vertical holds, “Separated by a complete compartment or hold from” means that separate holds are required. On barge-carrying vessels having horizontal barge levels, separate barge levels are required and the barges may not be in the same vertical line.

(4) “Separated longitudinally by an intervening complete compartment or hold from” means, for barge-carrying vessels with vertical holds, that separation by an intervening hold or engine room is required. On barge-carrying vessels having horizontal barge levels, separate barge levels and a longitudinal separation by at least two intervening barge spaces are required.

(k) Segregation requirements for ferry vessels: A ferry vessel (when operating either as a passenger or cargo vessel) that cannot provide the separation required in this section may carry incompatible hazardous materials in separate transport vehicles if they are stowed to give the maximum possible separation.

(l) Segregation of containers on board hatchless (open-top) container ships: (1) This paragraph applies to the segregation of cargo transport units that are transported on board hatchless container ships provided that the cargo spaces are properly fitted to give permanent stowage of the cargo transport units during transport.

(2) For container ships that have both hatchless container spaces and other spaces suitable for breakbulk cargo, conventional container stowage, or any other method of stowage, the appropriate requirements of this section apply to the relevant cargo space.

(3) Segregation Table. Table § 176.83(l)(3) sets forth the general requirements for segregation of cargo transport units on board hatchless container ships.

(4) In Table § 176.83(l)(3), a container space means a distance of not less than 6 m (20 feet) fore and aft or not less than 2.5 m (8 feet) athwartship.

(m) Provisions for segregation groups: (1) For the purpose of segregation, materials having certain similar chemical properties have been grouped together in segregation groups. The segregation groups (such as “acids”, “chlorates”, “permanganates”) and the entries allocated to each of these groups include the substances identified in section 3.1.4 of the IMDG Code (IBR, see § 171.7 of this subchapter). When column (10B) of the § 172.101 Table refers to a numbered stowage provision set forth in § 176.84(b) such as “Stow ‘away from’ acids”, that particular stowage/segregation requirement applies to all the materials allocated to the respective segregation group.

(2) Not all hazardous materials falling within a segregation group are listed by name in the regulations. These materials are shipped under “n.o.s.” entries. Although these “n.o.s.” entries are not listed themselves in the above groups, the person who offers a hazardous material for transportation must decide whether allocation under a segregation group is appropriate.

(3) The segregation groups described above do not address materials that fall outside the classification criteria of the hazardous materials regulations, although it is recognized that some non-hazardous materials have certain chemical properties similar to hazardous materials listed in the segregation groups. A person who offers a hazardous material for transportation or the person responsible for packing the materials into a cargo transport unit who does have knowledge of the chemical properties of such non-hazardous materials may identify a relevant segregation group and apply the segregation requirements for that segregation group.