Hazard class · ADR 2025

Class 4.1 — flammable solids, self-reactive substances, polymerizing substances and solid desensitized explosives

Readily combustible solids, self-reactive substances and solid desensitised explosives that can ignite through friction or contact with a spark.

Packing groups: I–III
UN entries: 137

Buy Class 4.1 package labels Buy Class 4.1 placards Check your UN number

What belongs in this class?

Class 4.1 covers flammable solids, solid desensitized explosives, self-reactive liquids or solids and polymerizing substances. (ADR 2.2.41.1.1)

In practice that means five families — readily flammable solid substances and articles, self-reactive solids or liquids, solid desensitized explosives, substances related to self-reactive substances, and polymerizing substances. (ADR 2.2.41.1.1)

A powdery, granular or pasty substance (metal powders aside) is treated as a readily flammable solid if it ignites easily on brief contact with an ignition source, or if once ignited the flame spreads with a burning time under 45 seconds over 100 mm. Metal powders qualify if a flame ignites them and the reaction spreads over the whole sample within 10 minutes. (ADR 2.2.41.1.5)

Classification rules

ADR 2.2.41.1.2
The class is subdivided by classification code — F for flammable solids (F1 organic, F2 organic molten, F3 inorganic, F4 articles), plus FO oxidizing, FT toxic, FC corrosive, D and DT for solid desensitized explosives, SR for self-reactive substances and PM for polymerizing substances.
ADR 2.2.41.1.2
Self-reactive substances and polymerizing substances are further split into those requiring temperature control (SR2, PM2) and those that do not (SR1, PM1).
ADR 2.2.41.1.5
Solids that may cause fire through friction (matches, for example) are classified by analogy with existing entries or under a special provision.
ADR 2.2.41.1.7
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.

Packing groupUN numbers

IPacking group I28

IIPacking group II34

IIIPacking group III51

Flammable solids are assigned to packing group II or III — there is no packing group I — on the basis of the burning-rate tests in the Manual of Tests and Criteria. (ADR 2.2.41.1.8)

For readily flammable solids with a burning time under 45 seconds over 100 mm, the wetted-zone test decides — PG II if the flame passes the wetted zone, PG III if the wetted zone stops the flame for at least four minutes. For metal powders, PG II if the reaction spreads over the whole sample in five minutes or less, PG III if it takes longer. (ADR 2.2.41.1.8)

Class 4.1 in Table A

Transport categories, tunnel codes and quantity reliefs across the 137 Table A entries of this class.

Transport categories

Category 144

Category 241

Category 342

Category 47

No category3

The category feeds the 1.1.3.6 calculation — the lower the number, the stricter the limit.

Tunnel codes

E72

B38

D24

—3

The column 15 code decides which tunnel categories the load may pass.

Limited quantities (LQ)

entries allow LQ

of 137 in the class

For the rest there is no relief — the full ADR applies to any quantity.

Excepted quantities (EQ)

entries allow EQ

of 137 in the class

For the rest there is no relief — the full ADR applies to any quantity.

Exact values by UN number Calculate the 1.1.3.6 exemption Tunnel restrictions

Marking and signs for Class 4.1

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).

Buy the 100 × 100 mm label Package marking explained

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).

Buy the 250 × 250 mm placard Placards and orange plates

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).

Buy the LQ mark How limited quantities work

Class 4.1 specifics

ADR 5.2.2.1.9
The label conforming to model No. 4.1 also implies that the product may be flammable, hence no label conforming to model No. 3 is required.
ADR 5.2.2.1.9
For self-reactive substances Type B a label conforming to model No. 1 must in addition be applied, unless the competent authority has permitted it to be dispensed with for a specific packaging on the basis of test data.
ADR 5.2.2.1.9
For self-reactive substances mentioned by name, the labels to be affixed are indicated in the list in 2.2.41.4.

Transport document

What must be written in the transport document when you ship Class 4.1 goods.

ADR 5.4.1.1.1
The transport document entry follows the general rule with the packing group — for example, UN 1350, SULPHUR, 4.1, PG III, (E).
ADR 5.4.1.2.3.1
For self-reactive and polymerizing substances that require temperature control, the document must indicate "Control temperature: ... °C Emergency temperature: ... °C".
ADR 5.4.1.2.3.2
When the competent authority has permitted the label conforming to model No. 1 to be dispensed with for a specific packaging, the document must include the statement "The label conforming to model No. 1 is not required".
ADR 5.4.1.2.3.3
When self-reactive substances are carried under conditions where approval is required, a statement to this effect must be included and a copy of the competent authority approval with the conditions of carriage attached.
ADR 5.4.1.2.3.5
When self-reactive substances type G are carried, the statement "Not a self-reactive substance of Class 4.1" may be given in the document.