Classification of Aerosol
Pipeline and Hazardous Materials Safety Administration · May 1, 1998 · Reference No. 98-0403
Reggie’s quick take
A shipper asked whether a 16-ounce can holding carbon dioxide and trichloroethylene, to be shipped by vessel under the IMDG Code, can be classed and described as an "Aerosol." PHMSA said that the shipper must make the classification itself under § 173.22, and that based on the safety data sheet, the material is "Aerosol, Division 2.2" (nonflammable gas). For vessel shipments under the IMDG Code, cans of 1000 ml or less may use the limited quantity description "Aerosols, Class 2, UN 1950, Limited Quantity" and may be marked "AEROSOLS" instead of the nonflammable gas label, under Section 18 of the IMDG Code.
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 regarding the classification of an aerosol containing carbon dioxide and trichloroethylene in 16 ounce cans for shipment by vessel in accordance with the International Maritime Dangerous Goods (IMDG) Code. You asked if you are correct in classifying and describing the material as an "Aerosol". I apologize for the delay in responding and hope it has not caused any inconvenience.
Under 49 CFR 173.22, it is the shipper's responsibility to properly classify a hazardous material. This office does not perform that function. Based on the information you provided on the Material Safety Data Sheet enclosed with your letter, it is the opinion of this Office that your material is an "Aerosol, Division 2.2" (nonflammable gas). Under the HMR, aerosols must comply with the requirements in 49 CFR 173.306(a)(3). The following description applies:
"Aerosols, 2.2, UN 1950, Limited Quantity"
Under the HMR., with certain exceptions, if all or part of the transportation is by vessel, a hazardous material which is classed, packaged, marked, labeled, placarded and described in accordance with the requirements of the HvIDG Code may be offered and accepted, and transported in the United States (see 49 CFR 171.12(b)). The IMDG Code permits aerosols with a capacity not exceeding 1000 ml to be transported in accordance with the limited quantity provisions in Section 18 of the General Introduction of the IMDG Code. In that case. the following description and marking is appropriate:
"Aerosols. Class 2, UN 1950, Limited Quantity"
For 1000 m1 or less, package may be marked "AEROSOLS" (Instead of Non-flammable (Gas label)
You may wish to consult Section 18 of the IMDG Code for further information on excepted documentation on package marking.
For your information, in a final rule published in the Federal Register under Docket HM215B [62 FR 24690; 05/06/97], in 49 CFR 171.8, the term "Aerosol" was defined. Aerosol means any non-refillable metal receptacle containing a gas compressed, liquefied, or dissolved under pressure, the sole purpose of which is to expel a nonpoisonous (other than a Division 6.1 Packing Group III material) liquid, paste, or powder and fitted with a self-closing release device allowing the contents to be ejected by the gas.
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.