Ask ten sellers whether a bottle of bleach needs a dangerous goods declaration, and most will say no — it lives under the kitchen sink, not behind a hazmat placard. Sodium hypochlorite dangerous goods classification disagrees. It is UN1791, hazard class 8, corrosive, and whether it lands in packing group II or III comes down to one figure almost nobody checks: the available chlorine percentage on the label.
This guide sets out that classification precisely, where the concentration line actually falls, and what changes once a product crosses it.
Why a cleaning product counts as a corrosive
Sodium hypochlorite solution — bleach, in every strength from a laundry bottle to a water-treatment drum — is regulated because it meets the Class 8 test for corrosivity: it destroys living skin tissue on contact, or corrodes steel and aluminium at a measurable rate. Both criteria are about the chemistry, not the marketing. A product sold as a gentle household disinfectant and one sold as an industrial descaler can carry the same underlying hazard, just at different strengths.
That distinction — strength, not identity — is what makes sodium hypochlorite dangerous goods classification genuinely dependent on a lab figure rather than on the product category. Two bottles labelled "bleach" can sit in different packing groups, and one weak enough may not be regulated at all.
UN1791 at a glance
| Field | Value | Note |
|---|---|---|
| UN number | UN1791 | Same across 49 CFR, IATA DGR and IMDG |
| Proper shipping name | Hypochlorite solution | Covers sodium and calcium hypochlorite solutions |
| Hazard class | 8 | Corrosive |
| Packing group | II or III | Set by available chlorine concentration |
| Label | Class 8 corrosive | Black-and-white corrosive symbol |
| Marine pollutant | Yes | Marine pollutant mark required for sea transport |
| ERG guide | 154 | Emergency response guide reference |
Compare that with the classes that never take a packing group at all — see the nine classes of hazardous materials for the full picture of which entries do and do not. UN1791 is not one of the exceptions: it always takes a group, and the group is never assumed.
Sodium hypochlorite dangerous goods classification by concentration
The packing group question reduces to a single question: how much available chlorine is in the solution? For how packing groups are set across every hazard class, see our guide to hazardous goods categories and packing groups I, II and III.
| Available chlorine | Packing group | Typical product |
|---|---|---|
| Roughly 3–8% | III | Retail laundry and disinfectant bleach |
| Roughly 8–16% | Confirm against SDS data | Concentrated commercial cleaning product |
| Above roughly 16% | II | Industrial and water-treatment strength |
Two things follow from that table. First, most household bleach — the familiar 5–8.25% available chlorine sold at retail — sits comfortably in packing group III. Second, a private label brand that reformulates toward a stronger "professional strength" claim can walk straight into packing group II territory without anyone deciding to change the classification on purpose. The label copy moved. The chemistry moved with it.
When a stronger claim changes the paperwork
A cleaning products brand sells a laundry bleach at 6% available chlorine for two years, packed and labelled correctly as UN1791, packing group III. Sales are steady on a marketplace that rewards concentrated, fewer-bottle formats, so the brand reformulates to a "2x concentrated" version at roughly 12% available chlorine to compete on shelf space and freight cost per unit sold.
Nobody on the product side flagged it as a compliance question — it read as a marketing decision, not a chemistry one. But 12% sits inside the band where the packing group genuinely depends on the measured figure rather than the old assumption, and the SDS that came back from the reformulated batch put it closer to packing group II once tested against the full criteria. The outer cartons, still rated for packing group III, were now under-specified, and the shipping papers carried the wrong group on every pallet that went out before the discrepancy surfaced during a routine carrier audit.
Concentration is the whole classification for a corrosive liquid. Two bottles with the same proper shipping name can sit in different packing groups, and the only honest source for which one applies is a measured figure, not the previous batch's paperwork.
Classify7 ruleset team
Limited quantities and the fee that changed the maths
UN1791 is eligible for the limited quantity exception, which relaxes some packaging, marking and documentation requirements for small retail-size containers — the exact per-package and per-outer limits are set out in the current 49 CFR 173.137 and the equivalent IMDG special provisions, and should be checked against the pack size you actually ship rather than assumed.
What has changed recently is the cost of skipping the declaration altogether. Since mid-2026, USPS applies a noncompliance fee of $50 to a commercial package found to contain hazardous materials that were not properly declared and labelled at the point of label creation — on top of the federal civil penalty framework under PHMSA's hazmat programme, which reaches six figures per violation for serious or repeated breaches. A bottle of concentrated bleach mailed as an ordinary parcel is exactly the kind of shipment that fee targets: cheap enough that nobody thought to check, common enough that the mail network sees it constantly.
Where carriers actually diverge
The regulatory position is one thing; what a given service will actually carry is another, and for a liquid corrosive the gap between them matters.
- UPS and FedEx accept properly classified, packaged and labelled hypochlorite solution on their ground and, within limits, air services, subject to their own dangerous goods guides.
- USPS accepts it under Publication 52's hazardous materials rules, with quantity limits and marking requirements set out there — and now the added exposure of the noncompliance fee if it goes out undeclared.
- Amazon FBA treats corrosive liquids as a reviewed category rather than an automatic acceptance, and inbound shipments are commonly held for hazmat review before they reach a fulfilment centre.
Sodium hypochlorite solution is also designated a marine pollutant under the IMO's IMDG Code, so an ocean shipment carries the marine pollutant mark alongside the Class 8 label — a requirement that has no equivalent on a road or air shipping paper, and one that is easy to miss when a business's existing hazmat process was built around parcel carriers rather than freight.
Our carrier-by-carrier hazmat comparison sets these positions out side by side, and the Amazon FBA hazmat review guide covers what a corrosive liquid submission actually needs to clear.
- Assuming every bleach product is packing group III without checking the actual available chlorine figure.
- Reformulating toward a stronger claim without re-running the classification.
- Omitting the marine pollutant mark on an ocean shipment.
- Treating the limited quantity exception as a blanket exemption rather than checking the pack size limits.
- Mailing an undeclared bottle and assuming a small parcel will not be checked.
Checking your own SKU
The determination needs one figure you almost certainly already have: the available chlorine percentage from your SDS or certificate of analysis. Send it to POST /api/classify alongside the product description and you get UN1791 back with the concentration-derived packing group, the marine pollutant flag, and the per-carrier position for the service you plan to use.
For the wider corrosives picture, see the nine classes of hazardous materials, or browse the encoded Class 8 entries to see what else shares the class. Household and industrial hypochlorite sit inside the same regulatory framework as every other corrosive — sodium hypochlorite dangerous goods classification is simply a concentration lookup once you have the number.
