PHMSA letter of interpretation

Letter "D" in Column 1 of the HMT

Pipeline and Hazardous Materials Safety Administration · Aug 7, 1992 · Reference No. 92-0109

PHMSA says to use caution with this letter. On January 8th, 2015, PHMSA published Final Rule HM-215M which amended the HMT entries for UN3268 and UN0503. To align with International regulations, the proper shipping name of Air bag inflators, or Air bag modules, or Seat-belt pretensioners was changed to UN3268, Safety devices, electrically initiated and UN0503, Safety devices, pyrotechnic. In addition, the packing group was removed for both entries.

Interprets: 49 CFR § 172.101

Reggie’s quick take

Someone asked PHMSA to change the "D" note in column 1 of the Hazardous Materials Table, § 172.101(b)(3), so it would cover international shipments to Canada, or to assign a new symbol for those shipments. The asker was seeking a Canadian exemption to ship air bag inflators and modules as flammable solids. PHMSA said the asker misread the note. The "D" marks names that are fine for domestic shipping but may not appear in the ICAO or IMDG international rules. It does not limit those names to domestic shipments.

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 reference to your letter dated July 7, 1992, requesting that the explanation for the letter "D," in 49 CFR 172.101(b)(3), be amended to include international shipments to Canada or that a new symbol be assigned to apply to shipments to and from Canada.

You state that you are in the process of obtaining from Transport Canada an exemption to encompass the provisions in the § 172.101 Hazardous Materials Table (the Table) and § 173.166 for the shipment of air bag inflators and modules as a flammable solid but the "D" in column 1 of the Table restricts application of those provisions to U.S. domestic shipments only.

We believe you misunderstand the intent of § 172.101(b)(3). Section 172.101(b)(3) states that the letter "D" identifies proper shipping names which are appropriate for describing materials for domestic transportation but may be inappropriate for international transportation under the provisions of the applicable international regulations. The intent of this provision is to alert shippers to the fact that, although these shipping names are acceptable for use in the U.S., these particular names may not be listed as proper shipping names in the International Civil Aviation organization's Technical Instructions for the Safe Transport of Dangerous Goods by Air or the International Maritime Dangerous Goods Code. It does not restrict usage of these names to domestic shipments only.

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.