Interpretation Response #25-0141
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: Thatcher Company of California
Individual Name: Ames Ettinger
Location State: CA Country: US
View the Interpretation Document
Response text:
March 9, 2026
Ames Ettinger
Laboratory Manager
Thatcher Company of California
8625 Unsworth Ave
Sacramento, CA 95828
Reference No. 25-0141
Dear Mr. Ettinger:
This letter is in response to your November 14, 2025 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the use of Department of Transportation (DOT)-4L welded insulated cylinders for the transportation of a 5% solution of "UN1833, Sulfurous acid, 8, PG II" in accordance with a packaging authorized in § 173.202. You explain that § 173.202(c) authorizes the following single packagings: "Cylinders, specification, as prescribed for any compressed gas, except for Specifications 8 and 3HT." In addition, you state while the requirements in § 173.202(c) do not explicitly prohibit the use of DOT-4L specification cylinders you ask whether these cylinders may still be used because they are designed for the transportation of liquefied gases and "UN1833" is a liquid hazardous material.
We have paraphrased and answered your questions as follows:
Q1. Is a DOT-4L cylinder an authorized cylinder specification under § 173.202(c) for the transportation of "UN1833"? If not, would this require submitting a special permit request to perform this function?
A1. Yes. Section 173.202 authorizes non-bulk packagings for transportation of liquid hazardous materials in Packing Group II. Thus, in accordance with § 173.202(c) which authorizes specification cylinders, and except for transportation by passenger aircraft, a DOT-4L cylinder adhering to applicable requirements of the HMR (e.g., § 173.24(b)) may be used for the transportation of a "UN1833" material.
Q2. If a DOT-4L cylinder is considered an authorized packaging under § 173.202, are the cylinders excepted from requalification requirements in accordance with § 180.209, even though they are used for a liquid?
A2. Yes. When a DOT-4L cylinder is used for liquid transport under § 173.202, it is considered an authorized packaging. Because DOT-4L cylinders are excluded from the requalification table listed in § 180.209(a), they are not subject to periodic requalification testing. However, this does not except the offeror or carrier from other HMR safety standards, such as the general inspection and maintenance requirements found in § 180.205(e).
I hope this information is helpful. Please contact us if we can be of further assistance.
Sincerely,
Dirk DerKinderen
Chief, Standards Development Branch
Standards and Rulemaking Division
§ 173.24(b), § 173.202, § 173.202(c), § 180.205(e), § 180.209, § 180.209(a)