IMDG Class 5.1 is the hazard subclass for oxidising substances, substances that release oxygen during decomposition or combustion and can dangerously intensify a fire involving other materials. The class covers nitrates, chlorates, perchlorates, hypochlorites, inorganic peroxides, and several specific oxidising acids. Common Chinese-export examples include sodium chlorate, calcium hypochlorite, hydrogen peroxide solutions above 20%, and various nitrate fertiliser intermediates.
What defines Class 5.1
A substance is Class 5.1 if it can release oxygen on contact with combustible material faster than a defined reference substance under standardised IMDG test conditions. The PG split:
| Packing group | Test result vs reference | Hazard severity |
|---|---|---|
| PG I | Reaction faster than 50% potassium bromate / cellulose mix | Highest danger |
| PG II | Reaction faster than 40% potassium bromate / cellulose mix | Medium danger |
| PG III | Reaction faster than 65% potassium bromate / cellulose mix | Lower danger |
PG I includes ammonium dichromate, sodium chlorate, and certain perchlorates. PG II includes calcium hypochlorite (commonly known as bleaching powder, UN 1748) and many ammonium nitrate-based fertilisers. PG III includes most aqueous hydrogen peroxide solutions and lower-concentration oxidising salts.
Common Class 5.1 chemicals exported from China
- Sodium chlorate (UN 1495, PG II), pulp and paper bleaching, herbicide intermediate. Major Chinese export from Shandong and Hebei.
- Calcium hypochlorite (UN 1748, PG II), water treatment, swimming pool chemical. Most-shipped halogen oxidiser from China.
- Hydrogen peroxide solution (UN 2014 for ≥20% to ≤60%, PG II; UN 2015 for >60%, PG I), pulp bleaching, electronics cleaning, antiseptic. The PG depends on concentration. Always confirm the exact concentration before booking, a buyer ordering “50% H2O2” gets UN 2014 PG II; a buyer who unknowingly accepts “70% H2O2” gets UN 2015 PG I, with stricter packaging and quantity limits.
- Potassium permanganate (UN 1490, PG II), water treatment, organic synthesis oxidant
- Sodium perborate (UN 3247, PG III), bleach booster in detergent formulations
Packaging requirements
Class 5.1 packaging must be UN-certified to the assigned PG. Hydrogen peroxide solutions ship in HDPE-lined drums with vented closures, the substance slowly decomposes and releases oxygen, so a sealed drum can over-pressurise. Calcium hypochlorite ships in steel drums or HDPE drums with desiccant additives to manage moisture-driven decomposition.
The vented closure requirement is a recurring quality issue. Some lower-tier Chinese factories ship hydrogen peroxide in non-vented closures and the buyer discovers swollen drums on arrival. If the swelling is severe the carrier may refuse discharge and the cargo is rerouted as damaged.
The strict segregation rules
Class 5.1 is one of the most segregation-restrictive classes in the IMDG system. Oxidisers can intensify any fire involving combustible material, so they must be stowed away from many other classes:
- “Separated from” Class 1 (explosives), Class 2.3 (toxic gases), Class 3 (flammable liquids), Class 4 (all subclasses), Class 5.2 (organic peroxides), Class 6 (toxic and infectious), Class 7 (radioactives), Class 8 (corrosives)
- “Segregated from” Class 1.5 blasting agents
In practice this means a 5.1 cargo cannot share a container with most other DG classes. For LCL consolidation the forwarder will often place 5.1 cargo in a dedicated container even at low fill rates, because mixing is prohibited.
Documentation chain and the China-side licensing layer
Standard DG documentation applies. Beyond that, several Class 5.1 substances are on the Chinese list of monitored chemicals and require an export licence in addition to the standard MEE DG declaration. Sodium chlorate and ammonium nitrate are routinely subject to extra licensing under China’s anti-terrorism precursor controls. Calcium hypochlorite has triggered precursor controls intermittently when public-safety incidents involving the chemical have occurred internationally.
A buyer contracting a new Chinese factory for any nitrate, chlorate, or perchlorate purchase should confirm:
- The factory holds a current dangerous-chemicals production licence
- The substance is not currently on the precursor-monitoring list (changes per-incident)
- The factory has shipped this UN number internationally in the past 12 months, a track record signal that licensing channels are open
Operator note: hydrogen peroxide concentration creep
A common quality issue with Chinese hydrogen peroxide is concentration drift between the COA and the actual shipped batch. The factory declares 50% concentration on the SDS and DG declaration. The COA shows 49.2% (within tolerance). The actual delivered concentration on lab test at destination shows 47.8%, out of the buyer’s spec but inside the SDS classification band, so no transport issue. The buyer’s downstream process is then under-treated. Always specify the lower concentration tolerance on the PO and require pre-shipment third-party titration testing for hydrogen peroxide above 35%.
Related terms
IMDG umbrella code. UN number for substance-specific identification. Packing group. IMDG Class 3, strict segregation against this. IMDG Class 4.1, also strict segregation. Segregation table for the full matrix.