Class 4.3 — substances which, in contact with water, emit flammable gases
Substances that react with water to release flammable gas — often in dangerous quantities and at a dangerous rate.
- Packing groups
- I–III
- UN entries
- 127
What belongs in this class?
Class 4.3 covers substances that react with water to emit flammable gases liable to form explosive mixtures with air, and the articles that contain them. (ADR 2.2.43.1.1)
A substance falls into the class when, in testing, the gas it emits ignites spontaneously at any step, or when flammable gas evolves at a rate greater than 1 litre per kilogram of substance per hour. (ADR 2.2.43.1.5)
Because organometallic substances can land in Class 4.2 or 4.3 depending on their properties, a dedicated classification flow chart applies to them. (ADR 2.2.43.1.5)
Classification rules
- ADR 2.2.43.1.2
The classification code is built on the letter W — W for substances that only emit flammable gases (W1 liquid, W2 solid, W3 articles), with WF flammable, WS self-heating, WO oxidizing, WT toxic, WC corrosive and WFC flammable-corrosive combinations.
- ADR 2.2.43.1.8
Water is the defining hazard, so the whole packing-group scale is driven by the rate at which each substance liberates flammable gas on contact with water.
- ADR 2.2.43.1.6
Where admixtures move a substance into a different hazard category than its named entry, the mixture is classified on its actual degree of danger.
Packing groups in this class
How many UN numbers in this class fall under each packing group.
Class 4.3 substances are assigned to packing group I, II or III according to how vigorously they react with water and how fast flammable gas is produced. (ADR 2.2.43.1.8)
- PG I — reacts vigorously with water at ambient temperature, tending to make the gas ignite spontaneously, or evolves flammable gas at 10 litres per kilogram or more over any one-minute period. (ADR 2.2.43.1.8)
- PG II — reacts readily with water so that the maximum rate of flammable-gas evolution is 20 litres per kilogram per hour or more, without meeting PG I. (ADR 2.2.43.1.8)
- PG III — reacts slowly, with the maximum rate of flammable-gas evolution above 1 litre per kilogram per hour, without meeting PG I or II. (ADR 2.2.43.1.8)
Class 4.3 in Table A
Transport categories, tunnel codes and quantity reliefs across the 127 Table A entries of this class.
Transport categories
The category feeds the 1.1.3.6 calculation — the lower the number, the stricter the limit.
Tunnel codes
The column 15 code decides which tunnel categories the load may pass.
Limited quantities (LQ)
entries allow LQ
of 127 in the class
For the rest there is no relief — the full ADR applies to any quantity.
Excepted quantities (EQ)
entries allow EQ
of 127 in the class
For the rest there is no relief — the full ADR applies to any quantity.
Marking and signs for Class 4.3
What must be on every package — and what the transport unit carries on the road.
On the package
Every package carries the danger label of its Table A entry and the UN number with the letters "UN" (ADR 5.2.1, 5.2.2).
On the transport unit
Orange plates at the front and rear — and for tanks and bulk also enlarged placards 250 × 250 mm on the sides and rear (ADR 5.3.1, 5.3.2).
Limited quantities
Goods packed under Chapter 3.4 carry the LQ mark instead of the danger label and UN number (ADR 3.4.1, 3.4.7).
Class 4.3 specifics
- ADR 5.2.1.10.1
If the inner packagings of a combination packaging contain liquids, the package must bear orientation arrows — a general rule that applies to goods of all classes.
Transport document
What must be written in the transport document when you ship Class 4.3 goods.
- ADR 5.4.1.1.1
The transport document entry shows the packing group, which may be preceded by the letters PG — for example, UN 1428, SODIUM, 4.3, PG I, (B/E).
- ADR 5.4.1.1.6.2.1
For empty packagings, uncleaned, the information of the goods last loaded may be replaced by "WITH RESIDUES OF " followed by the classes and subsidiary hazards in the class numbering order.
- ADR 5.4.1.1.3.2
For wastes, the estimation of quantity is not allowed for substances of Class 4.3 — the exact quantity is required.
Reliefs and restrictions
How much may travel under lighter regimes — and where tunnels restrict the route — is set per UN entry in Table A.
Limited quantities (LQ)
Column 7a caps each inner packaging. Within Chapter 3.4 most ADR requirements fall away, including the driver certificate.
ReadExcepted quantities (EQ)
E codes in column 7b let very small inner receptacles travel with almost no ADR overhead (Chapter 3.5).
ReadTunnel restrictions
Column 15 assigns the tunnel restriction code — it decides which tunnel categories the load may pass.
ReadLook up a Class 4.3 UN number
Get the full ADR profile for any UN number in this class.
Typical UN numbers
All 127 entries
Help with Class 4.3 shipments
Not sure this class applies to you?
A DGSA can confirm the classification before your next load leaves the yard.
Train your team
Awareness training under ADR 1.3 for everyone who consigns, packs or loads dangerous goods.
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