Hazard Class 5 — Oxidising Substances & Organic Peroxides
Substances that release oxygen or otherwise drive combustion in other materials.
Overview
Class 5 covers two related hazards. Division 5.1 oxidisers do not necessarily burn themselves but release oxygen or otherwise intensify the combustion of other materials. Division 5.2 organic peroxides are thermally unstable substances that can decompose rapidly with heat release.
Many 5.2 entries require temperature control during transport and carry stringent passenger-aircraft restrictions.
Divisions within Class 5
| Division | Description |
|---|---|
| 5.1 | Oxidising substances |
| 5.2 | Organic peroxides |
Aviation context
The most recognisable Class 5 article in aviation is the chemical oxygen generator (UN3356) used in passenger emergency oxygen systems. Improper handling of these devices has historically been the cause of major aviation incidents, and they are strictly regulated.
Hydrogen peroxide solutions appear in some specialised cleaning and component overhaul processes and must be classified carefully — the concentration drives the packing group.
Typical UN numbers in aviation MRO
| UN Number | Proper Shipping Name | Notes |
|---|---|---|
| UN3356 | Oxygen generator, chemical (5.1) | Passenger emergency oxygen — strict rules apply |
| UN2014 | Hydrogen peroxide, aqueous solution (5.1, subsidiary 8) | Concentration determines PG |
| UN1942 | Ammonium nitrate (5.1) | Rare in MRO but used in some chemical processes |
Packaging and marking essentials
- PI for chemical oxygen generators requires the device to be in a serviceable, packaged condition with all initiation devices fully secured.
- Organic peroxides under temperature control require qualified packaging and an emergency response plan from the operator.
- Subsidiary risk labels (often Class 8) must be applied when present.
Frequently Asked Questions
Why are chemical oxygen generators so tightly regulated?
Their accidental activation generates oxygen and significant heat. The 1996 ValuJet 592 accident, caused by mis-shipped chemical oxygen generators, drove much of the current strict regime around UN3356 and Class 5.1 in air transport.
Does a 35% hydrogen peroxide solution travel as PG II or PG III?
Concentration thresholds determine the packing group. Below 40% and above 8% concentration is commonly assigned PG II under UN2014, but always verify against the current IATA DGR Table 4.2 — the cut-offs are precise.
Need to classify a specific part?
DG Copilot identifies the UN number, hazard class and air transport status from a part number — in seconds.
Other hazard classes
This information is provided for guidance only. Always verify against the current IATA DGR edition. Final classification and DGD must be validated by a certified DG specialist.