§ 05.4Size Guide / UN & DOT Ratings
31HA1,
decoded character
by character.
The marking plate on an IBC cage is the most information-dense label in industrial packaging and almost nobody reads it properly. Every character means something specific, and knowing what means you can verify a supplier's claims instead of trusting them.
- Standard
- UN Model Regs / 49 CFR
- Common type
- 31HA1
- Periodic test
- 30 and 60 months
- Marking location
- Plate on the cage
§ 05.4.1The design type code
Four characters, four facts.
Everything before the slash is the design type. It tells you what the container is made of and what it may carry.
31
Category
Rigid IBC intended for liquids. A 11 prefix would mean solids discharged by gravity; 21 means solids discharged under pressure.
H
Inner material
Plastic. A means steel, B aluminium, N other metal, G fibreboard, L textile, M paper, D plywood.
A
Outer material
Steel outer frame. Z would mean a composite with a different outer material; absent means no outer.
1
Design feature
Non-pressurised design. A 2 indicates a pressurised design type, which composite IBCs for general liquid service are not.
| Code | Contents | Inner | Outer | Pressurised | Typical unit |
|---|---|---|---|---|---|
| 31HA1 | Liquids | Plastic | Steel | No | Standard composite IBC — the one you know |
| 31HZ1 | Liquids | Plastic | Other material | No | Composite with non-steel outer |
| 31HZ2 | Liquids | Plastic | Other material | Yes | Pressurised composite variant |
| 31H1 | Liquids | Plastic | None | No | Rigid plastic IBC without a cage |
| 31A | Liquids | Steel | — | No | All-steel IBC, including stainless |
| 31B | Liquids | Aluminium | — | No | Aluminium IBC |
| 11HA1 | Solids, gravity discharge | Plastic | Steel | No | Composite IBC for powders |
| 21HA1 | Solids, pressure discharge | Plastic | Steel | Yes | Pressure-discharge solids IBC |
§ 05.4.2The full marking string
Reading the whole plate.
The design type is only the beginning. A compliant marking carries nine or more elements, and each one is a checkable fact.
Example marking
UN / 31HA1 / Y / 03 25 / USA / M4821
1800 / 2418 / 1040 / 125
Marking layout varies between manufacturers but the elements are standardised. Read them in order and every one tells you something specific.
| Element | Example | Meaning |
|---|---|---|
| UN symbol | UN | Certifies conformity to the UN Model Regulations |
| Design type | 31HA1 | Composite IBC, plastic inner, steel outer, non-pressurised |
| Packing group | Y | Approved for packing groups II and III |
| Manufacture date | 03 25 | March 2025 — month and year |
| State of approval | USA | Country whose competent authority approved the design type |
| Manufacturer / approval ref | M4821 | Manufacturer mark and approval number |
| Stacking test load | 1800 | Permitted superimposed load in kg during stacking |
| Max gross mass | 2418 | Maximum gross mass in kg or lb as marked |
| Capacity | 1040 | Nominal capacity in litres |
| Tare | 125 | Tare mass, units as marked |
Reconditioned and recertified units carry additional marking indicating the reconditioner and the date of the most recent periodic inspection. That is the part worth checking on used stock.
| Letter | Packing groups | Hazard level |
|---|---|---|
| X | I, II and III | High — approved for the most hazardous |
| Y | II and III | Medium — the common IBC rating |
| Z | III only | Low |
Almost all composite IBCs are Y-rated. An X-rated composite IBC is unusual; packing group I liquids are more commonly shipped in steel.
Periodic inspection intervals
- Every 30 months
- External inspection, leakproofness test, check of service equipment and markings
- Every 60 months
- Full inspection including internal examination, leakproofness and structural assessment
- After repair
- Inspection and test before return to hazmat service
- Record
- Date of most recent test marked on the unit
An IBC used for hazardous materials transport whose periodic inspection has lapsed is not legally usable for that purpose, regardless of its physical condition. Check the date.
§ 05.4.3The limits of a rating
A valid marking is necessary, not sufficient.
This is where buyers get into trouble. A 31HA1/Y marking certifies that the design type passed drop, leakproofness, hydraulic pressure, stacking and vibration testing, and that this unit conforms to that design type.
It says nothing about chemical compatibility with your product, nothing about food contact, nothing about what was in it before and nothing about whether it has been cleaned. Those are separate questions with separate evidence.
We spell out exactly what our own recertification covers — and what it deliberately does not — on the certifications page, because conflating these is how a buyer ends up with a legally-marked container that is wrong for their material.
- Verify the design type suits the contents category — liquids versus solids
- Verify the packing group letter covers your material's packing group
- Verify the periodic inspection date has not lapsed
- Verify max gross mass exceeds your filled weight
- Separately verify chemical compatibility — the marking will not help you here
What a marking does not tell you
- Whether it is compatible with your specific product
- Whether it is suitable for food contact
- What was in it previously
- Whether it can hold pressure in storage
- Whether it has been washed, or how
- Whether it will pass its next periodic inspection
§ 05.4.4Rating questions
Compliance in practice.
Can a reconditioned tote carry a valid UN marking?
Yes, where it has been inspected and tested by a competent reconditioner and the periodic inspection record is current. The marking indicates the reconditioner and the test date. Our recertification process is described on the certifications page.
What happens if the periodic inspection has lapsed?
The unit cannot legally be used to transport hazardous materials until it is re-inspected and re-tested. It remains perfectly usable for non-regulated liquids and for storage. We can perform the inspection as part of our reconditioning service.
Does a Y-rated tote cover packing group I?
No. Y covers packing groups II and III only. For packing group I you need an X-rated design type, which is uncommon in composite IBCs — those materials are more usually shipped in steel.
Can I remove or cover a UN marking?
You must not leave a misleading marking on a container that no longer conforms. If a unit is being taken out of regulated service permanently, the marking should be removed or obliterated. We do this on units that leave our reuse path.
Is DOT the same as UN?
In the United States, 49 CFR adopts the UN Model Regulations for IBC design types, so the marking is the same and the requirements align. “DOT-rated” in common usage means the UN marking is recognised for domestic US transport.
Where exactly is the marking?
On a metal or durable plastic plate attached to the steel cage, usually on an upper horizontal member on one of the long faces. It is not moulded into the bottle — the bottle carries capacity and date markings only.
Send us the string
Photograph the marking plate and we'll decode it for you.
Including whether its periodic inspection is current and whether it covers the material you have in mind.