Segregation and Separation Chart of Hazardous Materials
Pipeline and Hazardous Materials Safety Administration · Dec 9, 2008 · Reference No. 08-0201
Interprets: 49 CFR § 173.12, 49 CFR § 177.848
Reggie’s quick take
Someone asked how to meet the separation rule for materials marked "O" on the segregation chart (49 CFR 177.848(e)(3)) when they are on the same vehicle. The agency said there is no set minimum distance, but it considers 4 feet in all directions acceptable. Barriers, non-hazardous freight, or open space also work, as long as the contents would not mix if packages leaked during normal transport. A bag of vermiculite between a flammable liquid drum and an oxidizer drum counts only if it actually keeps the materials from mixing if a leak happens. For a lab pack with a plastic liner inside a drum, the agency said no. The packaging itself cannot serve as the separation barrier.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This is in response to your letter dated July 30, 2008, regarding methods of achieving separation of hazardous materials, as indicated by the letter "O" in the Segregation and Separation Chart of Hazardous Materials (49 CFR 177.848(e)(3)), on the same transport vehicle in a manner that under conditions normally incident to transportation, commingling would not occur.
Your questions are paraphrased and answered as follows:
Q. In §177.848(e)(3), the "O" in the table indicates that the materials must be separated to prevent commingling if packages were to leak. In previous letters on this subject, you suggest that physical space is considered an acceptable method of separation. Is there a minimum distance that is considered acceptable?
A. The requirement for separation or non-adjacent loading is considered satisfied if the packages are separated in such a manner (for example, by using barriers, packages of non-hazardous materials, or intervening space) that their contents would not commingle in the event of leakage under conditions normally incident to transportation. There is no minimum distance specified, but, in our opinion, a distance of four (4) feet in all directions would be considered acceptable.
Q. Vermiculite is a material commonly used in packaging chemicals for cushioning and absorption of any spilled liquids in the event the inner container breaks. If a drum of Class 3 (flammable liquid) and a drum of Division 5.1 (oxidizer) were loaded onto a truck with a bag of vermiculite (with sufficient volume to absorb the liquid content of either drum) placed between these containers, would this be considered proper separation?
A. Section 177.848(e)(3) requires that separation must be accomplished by some means of physical separation, such as, non-permeable barriers, non-reactive freight, or non-combustible, non-reactive adsorbents between packagings of hazardous materials required to be separated; a bag of vermiculite placed between these containers would be acceptable only if it prevents commingling of materials in the event of leakage.
Q. Your company, Triumvirate Environmental, creates a lab pack that meets the lab pack provisions prescribed in §173.12(b); your company adds a 6 mil HDPE bag as a liner on the inside of the drum and vermiculite regardless if the inner containers have solids or liquids in them. The purpose of the liner is to provide additional "leak-proofing" in the event that one of the inner packages breaks open. In these lab packs, the inner packages are surrounded by absorbent material and placed in a leak-proof bag, which is then placed in a Packing Group II rated container. Would this packing method be considered adequate separation as prescribed in §177.848(e)(3)?
A. No. As previously stated, separation must be accomplished by some means of physical separation, such as non-permeable barriers, non-reactive freight, or non- combustible, non-reactive adsorbents between packagings of hazardous materials required to be separated. The mere integrity of a packaging may not be used as a physical barrier. If the packaging should fail, commingling of materials could not be prevented. Therefore, the packaging itself may not be used to satisfy the requirements of §177.848(e)(3).
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.