Transportation of Dangerous Goods (TDG): Overpack & Markings Legislation Changes

By Corie Doyle
Last updated: April 12, 2022
Key Takeaways

SOR/2014-159 came into force January 15, 2015. This is what it means for you.

Transporting raw materials is crucial to the production and marketing of a variety of products in the chemical, industrial, agricultural, and fuel sectors. Many of these materials are hazardous or dangerous in nature, requiring special handling during transportation.


The purpose of the Transportation of Dangerous Goods (TDG) Act and Regulations is to promote public safety when dangerous goods are being handled, offered for transport, or transported.

Compliance with TDG

Compliance with TDG is required for anyone handling (shipping, transporting, or receiving) dangerous goods by road, rail, air, or marine transport.


There are three main groups of people who must comply with the TDG Act:

  • Consignors, including the sender of the dangerous goods with their name on the shipping documents or has possession of the said dangerous goods immediately before shipping, such as manufacturers and distributors
  • Carriers, including anyone transporting dangerous goods such as trucking, marine shipping, and air cargo companies
  • Consignees, including anyone who receives dangerous goods from a consignor or carrier

Overpack and TDG Regulations

Overpack refers to an enclosure used by a single consignor to consolidate one or more small means of containment for ease of handling but that is not a minimum required means of containment. This definition does not include a large means of containment or a unit load device (ULD), as defined in the International Civil Aviation Organization (ICAO) Technical Instructions, which is intended for transport by Aircraft.

The International Air Transport Association's (IATA) Appendix A defines overpack as:

"An enclosure used by a single shipper to contain one or more packages and to form one handling unit for convenience of handling and stowage. Dangerous goods packages contained in the overpack must be properly packed, marked, labeled, and in proper condition as required by these regulations. Note: Shrink-wrap or banding may be considered an overpack.”

Examples of overpacks include:

  • A pallet holding one or more small means of containment that are secured by a strap, shrink wrap, stretch wrap, nets, or other similar means
  • A disposable box, crate, or bin holding one or more small means of containment

All modes of transport have the same definition of overpack:

  • Air (IATA)
  • Water (IMDG – International Maritime Dangerous Goods)
  • Ground (TDGR & 49CFR – United States Code of Federal Regulations)

Safety Marks for TDG for Overpack

The following is taken from Regulations Section 4.10.1 of Dangerous Goods Safety Marks, TDG Regulations for safety marks on an overpack.

  1. When a safety mark is required by this Part to be displayed on a small means of containment and the small means of containment is inside an overpack, the person who prepares the overpack must display:
    1. The word ‘Overpack’ or ‘Suremballage’, in letters that are at least 12mm high on a contrasting background, on at least one side of the overpack;
    2. The information required by subsection (3) on one side of the overpack, if its capacity is less than 1.8 cubic meters (64 cubic feet); and
    3. The information required by subsection (3) on two opposite sides of the overpack, if its capacity is greater than or equal to 1.8 cubic meters (64 cubic feet).
  2. Paragraphs (A) (2) and (3) do not apply if the safety mark on the small means of containment is visible through the overpack. (The word ‘overpack’ has to be put on all overpacks even if all the safety marks are visible.)
  3. The following information must be displayed on the overpack:
    1. The primary class label and each subsidiary class label for each of the dangerous goods contained in the overpack, except that only one label is required for dangerous goods that are included in the same class; and
    2. The shipping name and UN number of the dangerous goods.

Differences in Dangerous Goods Regulation

49 CFR, IATA Dangerous Goods Regulations (DGR), IMDG Code, UN Recommendations insert the words "representative of" in the overpack. The wordings of each regulation varies, so one has to be careful with the interpretation. IATA regulations in state that unless all markings representative of all dangerous goods in the overpack are clearly visible, the overpack must be marked with the word "overpack" in lettering at least 12 mm high and the package marks must be reproduced on the outside of the overpack.

I asked Brendan Sullivan, Head of Cargo Operations at IATA, for clarification about the use of "representative" and this was his reply:

"The intention is that only one box and the relevant marks are required (assuming they are identical). However, it starts to get a little complicated with UN Specification Packages, it would be impossible to tell whether the UN Specification marking you can see is ‘representative’ of the dangerous goods marking within the package. Previously we had packages inside comply with prescribed specifications, which was a clearer indication, but that is now gone. So I think that for an overpack of UN Specifications packages, you are either going to have to have all the UN Spec marks visible and the other package marks representative, or you will need to show ‘overpack’ on the outside."

49 CFR regulations and IMDG regulations are similar to this statement. The overpack is marked with the word "overpack," the proper shipping name, and UN number and is labeled as required for each dangerous good contained therein unless markings and labels representative of each hazardous material in the overpack are visible.

49 CFR requires an "overpack" mark only when DG packages in the overpack which requires a UN specification packaging do not have the marks visible from the outside of the overpack.

IATA DGR and IMDG Code require the word "overpack" to be applied if the DG safety marks are not visible from the outside of the overpack.

TDGR 4.10.1 (1) (marks on small means of containment) implies that markings on each package must be visible to avoid the need to reproduce them on the overpack. It also requires the use of an overpack mark regardless of the type of overpack whenever the safety marks are not visible from the outside of the overpack.

TDG and 49 CFR both require safety marks on two opposite sides if the overpack volume is 1.8 cubic meters or more, this is not applicable to IATA and IMDG regulations.

The upright/orientations arrows are required on the overpack for liquids on all modes of transport except for the TDG Regulations.

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Written by Corie Doyle | Product Development Manager

Corie Doyle

Corie is a mom, wife, daughter, sister, and friend, and keeping her family and friends safe is the foundation for her passion for safety.

She began her career as a Nuclear Medicine Technologist in British Columbia, then moved into radiochemical production and safety.

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