Volumetric capacity on TC highway tanks


This bulletin covers important safety information about marking and filling highway tanks that transport dangerous goods.


This page does not change the Transportation of Dangerous Goods (TDG) Regulations.


This bulletin is for anyone who manufactures TC highway tanks and for those who fill these and other highway tanks with dangerous goods.

What you need to know

Recently, Transport Canada found that some registered facilities have been marking the wrong volumetric capacity on the data plates of newly made TC highway tanks. The mistakes were most common for tanks designed to carry Class 3, 4, 5, 6.1, 8, and 9 dangerous goods.

If the volumetric capacity on a metal identification plate isn’t marked correctly, the tanks can be accidentally overfilled, resulting in an unsafe tank level and a dangerous goods spill.

Individuals filling these dangerous goods tanks must comply with the filling requirements in CSA B621.

Plate marking requirements

The manufacturing requirements for TC highway tanks intended for dangerous goods service are found in CSA B620. This standard outlines the metal identification plate markings for these tanks.

From CSA B620, Clause 3, Terminology and definitions:

Volumetric capacity — the maximum volume of water, normally expressed in litres, that a tank can hold at 15 °C and at an absolute pressure of 101.325 kPa.

The volumetric capacity of a tank is NOT the maximum volume of product that can be loaded into the tank.

Filling requirements

The maximum amount of dangerous goods that may be loaded into a tank carrying Class 3, 4, 5, 6.1, 8, and 9 dangerous goods must be determined per Clause 7.3 of CSA B621.

7.3 Loading requirements

During loading of a means of containment,


(d) If the means of containment is a tank, the outage left in the tank shall

  • (i) not be less than 2% of its volumetric capacity;
  • (ii) be sufficient to prevent the tank from becoming liquid-full should the temperature of the contents rise to 55 °C (131 °F); and
  • (iii) if the tank is to be placed, stored, or parked within an enclosed space, be sufficient to prevent venting should the temperature of the contents rise to 55 °C (131 °F).

A person loading TC highway tanks must ensure that these requirements are met when filling the highway tank. This will ensure that the tank cannot become liquid full while in transport. The filler will need to determine the maximum filling volume based on the volumetric capacity indicated on the metal identification plate, as defined in CSA B620.


If you have any questions, please contact our Regulatory Frameworks and International Engagement Branch:

Email: MOCRegister-RegistreContenant@tc.gc.ca
Phone: 1-855-298-1520 (toll free)