Classification of Restaurant Kitchen Fire Suppression Systems
Pipeline and Hazardous Materials Safety Administration · May 30, 2006 · Reference No. 06-0101
Interprets: 49 CFR § 173.309
Reggie’s quick take
Someone asked whether a restaurant fire suppression component is correctly listed for shipping as "Nitrogen, compressed, mixture, UN 1066." PHMSA said yes, and the full description is "Nitrogen, compressed, mixture, 2.2, UN 1066." The filled cylinder is shipped separately from the system, and the potassium carbonate inside is not regulated. The cylinder must still be marked, labeled and packaged as the rules require. The § 173.309 exceptions do not apply, because the cylinder is not set up to work as a fire extinguisher.
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 responds to your request concerning your company's line of restaurant kitchen fire suppression systems. One of the system components is a 4BW cylinder containing potassium carbonate and pressurized with nitrogen to 195 psi. The filled cylinder is packaged and transported as a separate component. You ask if "Nitrogen, compressed, mixture, UN 1066" is the correct shipping name and identification number under the Hazardous Materials Regulations (HMR; 49 CFR, Parts 171-180).
The answer is yes, the proper shipping description for the component is "Nitrogen, compressed, mixture, 2.2, UN 1066." The potassium carbonate is not a regulated material and is not subject to the HMR. The cylinder must be marked, labeled and packaged as prescribed. You may not take advantage of the exceptions in § 173.309 because the 4BW cylinder is not equipped to function as a fire extinguisher.
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.