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Interpretation Response #15-0136

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 03-29-2016
Individual Name: Mr. Edwin Van Schoick
Location state: FL    Country: US

View the Interpretation Document

Response text:

March 29, 2016

Mr. Edwin Van Schoick
18213 Bittern Avenue
Lutz, FL  33558

Reference No. 15-0136

Dear Mr. Van Schoick:

This is in response to your recent letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to transporting five Division 2.3 (poisonous) gases and one Division 2.2 (non-flammable) gas, all with subsidiary hazards.  We have listed the gases you described in the table below.  Specifically, you ask if these gases are segregated in the manner prescribed in § 177.848(e)(6) may they be transported on the same vehicle.  We have paraphrased your questions and answered them in the order you provided.  


ID No.

Hazardous Material

Primary Hazard

Subsidiary Hazard

Hazard Zone


UN 2188






UN 2199






UN 1953

Compressed gas, toxic, flammable, n.o.s.





UN 2418

Sulfur tetrafluoride





UN 2190

Oxygen difluoride, compressed


5.1, 8



UN 1070

Nitrous oxide




Q1. Do my Division 2.3 hazardous materials that have a Class 8 (corrosive) subsidiary hazard need to be segregated from other Division 2.3 hazardous materials when the Class 8 material is not in a liquid state since the segregation table in § 177.848 requires that Division 2.3 materials must be segregated from “8 liquids only”?

A1. The answer is no.  Division 2.3 hazardous materials with a Class 8 subsidiary hazard are not subject to the segregation requirements prescribed in § 177.848 for transportation in commerce by motor vehicle when no corrosive liquid is present.  In addition, § 177.848(e)(6) waives the segregation requirements for subsidiary “secondary” hazards in hazardous materials with the same primary hazard class provided these materials will not react dangerously with each other.

Q2. By segregating in a motor vehicle the materials meeting the Division 2.1 (flammable gas) subsidiary hazard class from the materials meeting the Division 5.1 (oxidizer) subsidiary hazard class, in my opinion a dangerous reaction between them would be eliminated by virtue of the fact that if there were simultaneous leaking containers of

these materials, both gases would be sufficiently diluted in concentration by the air in the transport vehicle.  The hazard of a dangerous reaction is posed by the air in the transport vehicle in the event of a leaking Division 2.1 subsidiary hazard material.  Can these materials be transported on the same transport vehicle if properly segregated?

A2. The segregation requirements in § 177.848(d) and (e) permit Division 2.1 materials to be placed in the same motor vehicle with Division 5.1 materials, but prohibit Division 2.3, Zone A, materials from being placed in the same motor vehicle with Division 5.1 materials.  However, § 177.848(e)(6) provides segregation relief by permitting materials with the same primary hazard regardless of their subsidiary hazards to be placed on the same motor vehicle provided they are not capable of reacting dangerously with each other and causing combustion or dangerous evolution of heat, evolution of flammable, poisonous, or asphyxiant gases, or formation of corrosive or unstable materials.  

I hope this satisfies your request.


T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division

177.848(e)(6), 177.848, 177.848(d)

Regulation Sections

Section Subject
§ 177.848 Segregation of hazardous materials