If you have ever looked at the data plate or molded marking on an IBC tote and seen a string of numbers and letters that looked like a foreign language, you are not alone. UN certification codes pack a tremendous amount of information into a compact format, and understanding how to read them is essential for anyone who transports hazardous materials or needs to verify that a container meets specific regulatory requirements.
At Grand Rapids IBC, we decode UN ratings for customers every day. Here is a complete guide to understanding what each element of the code means and why it matters.
The Basic Format
A typical UN marking on a composite IBC looks something like this: UN 31HA1/Y/1500/250/23/USA/MANUFACTURER/DATE. Each segment conveys specific information about the container type, construction, performance rating, and origin. Let us break down each element.
Container Type Code
The first part of the code identifies the container type. For composite IBCs, the code starts with 31H, where 31 indicates a rigid IBC for liquids and H indicates a composite construction (plastic inner with an outer framework). The letter that follows — A1, A2, B, etc. — specifies the outer cage material and whether the container has structural or non-structural outer packaging.
- 31HA1 — Composite IBC with a rigid plastic inner and a structural steel outer cage (most common)
- 31HA2 — Composite IBC with a rigid plastic inner and a structural aluminum outer cage
- 31HB1 — Composite IBC with a rigid plastic inner and a structural steel cage with stacking capability
- 31H1 — Rigid plastic IBC without an outer framework
- 21H1 — Rigid plastic IBC for solids
Packing Group Rating
The single letter following the type code indicates the packing group performance level. X means the container is rated for Packing Groups I, II, and III — the highest danger levels. Y means it is rated for Packing Groups II and III. Z means it is rated only for Packing Group III, the lowest hazard level. For non-hazardous materials, any rating will work, but for hazmat transport, you must match the packing group of your material to the container's rating.
Maximum Gross Mass and Stacking Load
The next two numbers indicate the maximum gross mass in kilograms and the stacking test load in kilograms. For a standard 275-gallon IBC, these are typically 1500 kg gross mass and 5600 kg stacking load. These figures are critical for safe handling and storage — exceeding either limit creates a risk of structural failure.
Manufacture Date and Origin
The final elements of the code identify the month and year of manufacture, the country of origin, and the manufacturer. The manufacture date is especially important for reconditioned IBCs because UN certification has a limited validity period. Composite IBCs used for hazardous materials must be requalified or taken out of hazmat service after five years from the date of manufacture.
If you need help decoding the UN markings on your IBC totes, the team at Grand Rapids IBC is always available to help. Bring a container to our facility or send us a photo of the data plate and we will walk you through every element of the code. Contact us to learn more.