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If you’re shipping hazmat and you can’t read the UN marking on a bulk bag, you’re basically driving at night with the headlights off.

Because the UN marking is the “passport” of the bag — it tells you what kind of packaging it is, what it’s approved for, and whether it’s even legal to use for your shipment.

And here’s the kicker:

Lots of people look at a UN mark and only see “UN.”
They don’t understand the rest of the code.

That’s how mistakes happen.

So in this article, you’ll learn how to read UN markings on bulk bags (UN rated FIBCs) in plain English, what each part generally means, what matters most for buyers, and how to avoid the common traps that lead to shipment rejections or compliance problems.

Quick note: This article is practical guidance, not legal advice. Always confirm requirements with your hazmat/transport compliance team based on your SDS and shipping classification.

First: what is a UN marking on a bulk bag?

A UN marking on a bulk bag is a standardized code that indicates the bag meets UN performance packaging requirements for dangerous goods.

It’s usually printed on the bag itself (often near the side seam) or on a tag/label that’s attached to the bag.

When you see a UN marking, you’re seeing the bag’s compliance identity.

It’s how:

carriers recognize it
auditors verify it
and you prove the bag was a compliant choice for dangerous goods packaging (assuming the rest of your shipment requirements are met)

But to use it correctly, you have to understand what the code is telling you.

The basic structure: a UN marking is a string of “clues”

Think of it like reading a VIN number on a vehicle.

Each chunk gives you information:

what type of package it is
what it’s made of
what hazard level it’s approved for (packing group rating)
what weight it’s approved to carry
when it was made
who made it
and where it was tested/approved

The exact formatting can vary slightly depending on region and marking style, but the same general pieces show up.

The piece buyers notice first: the FIBC type code (example: 13H3 or 13H4)

On UN rated bulk bags, you’ll often see a code like:

13H3
13H4

These are UN packaging type codes for FIBCs.

Here’s the plain-English version:

“13” = it’s a Flexible Intermediate Bulk Container (FIBC)

That’s the category: bulk bag.

“H” = it’s made of plastic (woven plastic)

In FIBC codes, the letter indicates the material type category. In practice, many UN FIBCs are woven polypropylene-based.

“3” vs “4” (the part people miss)

This part helps indicate whether the FIBC is designed to be used with a liner.

13H3 is commonly understood as a woven plastic FIBC without a liner
13H4 is commonly understood as a woven plastic FIBC with a liner

Why you care:
If your hazmat material is a fine powder or needs better containment, liners often matter. So “3 vs 4” is not trivia — it can be a critical compliance and performance detail.

The packing group rating: X, Y, or Z (hazard severity)

You’ll often see a letter like X, Y, or Z in UN packaging marks.

These letters relate to the Packing Group level the packaging is rated for:

X = approved for Packing Group I, II, and III (highest performance level)
Y = approved for Packing Group II and III
Z = approved for Packing Group III only

Think of it like this:

X is the toughest rating.
Y is middle.
Z is the lowest.

Important:
This doesn’t mean you should always buy X.

It means you must buy a bag rated appropriately for your shipment’s packing group requirement.

If your shipment is Packing Group I, a Z-rated bag is not the right choice.

The maximum gross mass (weight rating)

UN FIBC markings usually include a weight rating. This is often shown as a mass value (commonly in kilograms).

This is the maximum gross mass the bag is approved for:

product weight
plus bag and liner weight
plus any other packaging components

Why it matters:
A UN rated bag can become non-compliant in practice if you exceed the approved gross mass.

This is one of the most common real-world failures:

the bag is UN marked
but it’s overfilled

So when reading the marking, identify the mass rating and compare it to your target fill weight.

The year (or date) of manufacture

UN markings usually include a manufacturing year (often shown as the last two digits of the year or another recognizable format).

Why you care:
UN performance packaging has rules and expectations around:

service life and condition
whether packaging is in good condition at time of use
and whether markings are still legible

If you’re using bags that have been sitting around forever, even if they’re “new,” you can create questions during audits and inspections.

Bottom line:
The year helps you track inventory and avoid using old stock in sensitive programs.

The country code

UN markings often include a country code indicating the country of approval or manufacture/authorization.

This is typically a two-letter code (like a country code you’d see on vehicles or shipping docs).

Why you care:
It helps identify the approval authority region and can be relevant when shipments cross borders or when specific regulatory contexts apply.

The manufacturer or approval code

There is often a manufacturer identification code, facility code, or approval code included in the marking.

Why you care:
If there’s ever:

a recall
a quality event
a shipment incident
an investigation

…you need to identify who produced that bag and what lot it came from.

This is traceability, baked into the marking.

The test/approval reference (where applicable)

Some UN packaging marks include additional identifiers that link to:

test reports
design type approvals
certification references

Not every bag will present this in the same way on the face of the marking, but serious suppliers can support the marking with documentation.

If you’re using UN bags for hazmat, you should be able to request:

a Certificate of Conformance (COC)
lot traceability
and confirmation of UN certification for the bag design type

The marking is the label. The documentation is the proof behind it.

Putting it together: how to read it like a buyer

Here’s the practical reading sequence I recommend:

Step A: Identify the package type

Look for the FIBC type code:

Is it 13H3 or 13H4 (or another FIBC code)?
Does it match what you expected (lined vs unlined)?

Step B: Identify the packing group rating

Find X/Y/Z:

Does it match your packing group requirement?

Step C: Identify the maximum gross mass

Find the weight rating:

Can you legally and safely load your intended weight without exceeding it?

Step D: Identify manufacturing year and traceability info

Find year, country code, manufacturer code:

Can you trace it? Is it current enough? Are markings legible?

Step E: Confirm the marking is legible and on the bag

If the marking is faded, missing, or not on the actual bag, you have a problem.
In audits and incidents, “it was on the paperwork” isn’t always enough.

Common traps (and how to avoid them)

Trap #1: Assuming “UN” alone means the bag is correct

No. The rest of the code matters.

Trap #2: Buying a linerless UN bag for dusty powders when your program needs containment

For fine powders, lined bags are often the practical choice.

Trap #3: Ignoring packing group rating

If your shipment needs PG II, you can’t use a bag rated only for PG III.

Trap #4: Ignoring max gross mass

Overfilling can put you out of compliance.

Trap #5: Losing traceability internally

Even if the bag is properly marked, if you mix lots and don’t record which lot went to which shipment, you can’t defend your program in a quality event.

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What to request from suppliers (so you’re not guessing off a printed code)

UN markings are important, but you also want support documents.

For hazmat programs, request:

Certificate of Conformance (COC) per lot/shipment
lot/batch traceability for bags (and liners if included)
confirmation of UN certification for the design type
packing list that references lot numbers shipped
guidance on service life, storage, and handling requirements for the bags

This gives you a defensible paper trail.

Bottom line

To read UN markings on bulk bags, focus on the “big four” first:

FIBC type code (example: 13H3 vs 13H4) — tells you the general packaging type and often whether it’s intended to be lined
Packing group rating (X/Y/Z) — tells you what hazard severity level the packaging is rated for
Maximum gross mass — tells you how heavy you can legally load the bag
Traceability identifiers (year, country code, manufacturer/approval codes) — tells you whether you can defend and trace the packaging choice later

If you want, send the exact UN marking string you’re looking at (copy/paste it) and the SDS transport classification (UN number, hazard class, packing group, and target bag weight). I’ll translate the marking into plain English and tell you whether it matches what you need.