EN ISO 11612 – Clothing to protect against heat and flame
In short: EN ISO 11612 covers clothing that protects against heat and flame. Unlike high visibility or weather protection, there is no class number, but a series of code letters – each stands for a different type of heat exposure, each with its own performance level. Which code is on the label determines, in an emergency, whether the clothing covers the right hazard.
- The marking
- The flame in the shield identifies the garment as protective clothing against heat and flame. The pictogram is accompanied by the standard designation and the code letters with their performance levels.
- The symbol alone does not yet say what a garment protects against. Only the letters after it specify which types of heat exposure were tested – limited flame spread (code A) is mandatory, and there is always at least one further code from B to F. Two garments with the same pictogram can nevertheless cover completely different hazards. Which letter stands for what is explained under The code letters.
The code letters
Each letter stands for a test against a particular type of heat. Code A is mandatory, and at least one further code must also be met. For codes B to F, the digit indicates the performance level – the higher, the better; for A1 and A2, the digit stands for the ignition procedure, not for a level.
| Code | Test | Typical hazard |
|---|---|---|
| A1 | Limited flame spread, surface ignition | Jet of flame hits the surface |
| A2 | Limited flame spread, edge ignition | Flame attacks the hem or an edge |
| B | Convective heat | Hot air, heat build-up |
| C | Radiant heat | Furnace, molten material, embers nearby |
| D | Molten aluminium splash | Aluminium casting |
| E | Molten iron splash | Steel and iron casting |
| F | Contact heat | Touching hot surfaces |
Reading a code – using our collections as an example
This is what the codes look like in practice. The longer the string, the broader the hazard covered:
| Code | Covers | In our range |
|---|---|---|
| A1 B1 C1 F1 | Surface ignition, convective heat, radiant heat, contact heat | Basic multi-standard |
| A1 B1 C1 D1 E2 F1 | Additionally aluminium and iron splash | KÜBLER PROTECTIQ – the broadest code in the range |
| A1+A2 B1 C1 E3 | Surface and edge ignition, high level for iron splash | KÜBLER SAFETY X COMPACT |
| A1+A2 B1 C1 E3 F1 | As above, additionally contact heat | KÜBLER PROTECTIQ WELDING |
Inherent or finished – the difference lasts or fades
Flame protection is achieved in two fundamentally different ways:
- Inherent: The protection is in the fibre itself – as with aramid or modacrylic. It cannot be washed out and is retained over the entire service life.
- Finished: A normal fabric – usually cotton – is given a chemical flame-retardant treatment. The effect is real, but tied to the finish and therefore finite.
Our multi-standard fabrics are inherently flame-retardant: modacrylic, aramid and FR viscose blends, plus a proportion of antistatic fibre. The protection is therefore permanent – a point that tips the balance for rental laundry and long usage cycles.
In our multi-standard fabrics, the protective function is permanent – with the exception of chemical protection to EN 13034. That is based on a finish and not on a property of the fibre, making it the only one of the protective functions that is finite and dependent on washing. More on this on the page about EN 13034.
What matters in practice
The gap between the garments
Heat takes the path of least resistance. The most common weak point is not the material but the transition: between jacket and trousers, at the cuff, at the open collar. Protective clothing to EN ISO 11612 only works as a closed system – jacket over the trousers, sleeves rolled down, fastenings closed.
What is worn underneath matters too
Underwear made of polyester or other synthetic fibres can melt when exposed to heat and fuse with the skin – even under a protective jacket that complies with the standard. Flame-retardant underwear or natural fibres belong under flame protection.
For category III, customisation is a matter for the manufacturer
Flame-protective clothing is, as a rule, PPE category III. It may only be modified by the manufacturer, with notification to the test institute. A logo applied afterwards that is made of non-flame-retardant material can invalidate the certification – get in touch with us before any customisation is carried out.
Type-examination certificates expire
Under Regulation (EU) 2016/425, EU type-examination certificates are limited to a maximum of five years. For procurement, this means: with long-running framework agreements, it is worth looking at the date of issue of the certificate, not just at the number of the standard.
Collections with flame protection
39 styles from our collections are certified to EN ISO 11612 – jackets, trousers and bib and brace trousers, all with inherent flame protection.
Frequently asked questions
What do the letters A, B, C, D, E and F mean?
Each stands for a different type of heat: A for flame spread (A1 surface, A2 edge), B for convective heat, C for radiant heat, D for aluminium splash, E for iron splash, F for contact heat. Code A is mandatory, plus at least one other. The digit after B to F indicates the performance level.
Does all clothing to EN ISO 11612 protect against molten metal splash?
No. That expressly requires code D (aluminium) or E (iron). A garment with A1 B1 C1 is tested against flame and heat, but not against molten metal.
Does the flame protection wash out over time?
Not with inherently flame-retardant fibres such as aramid or modacrylic – there the property is in the fibre. With chemically finished cotton fabrics, the effect is tied to the finish and therefore has a limited life. Our multi-standard fabrics are inherently flame-retardant.
Which underwear should be worn under flame-protective clothing?
Flame-retardant underwear or natural fibres. Synthetic fibres can melt when exposed to heat and make burns considerably worse – even under a protective jacket that complies with the standard.
Can I have company logos applied?
Flame-protective clothing is usually PPE category III and may only be modified by the manufacturer, with notification to the test institute. A logo made of non-flame-retardant material can invalidate the certification. Clarify the customisation beforehand.
Advice on heat and flame protection
The code on the label
decides in an emergency.
We will go through with you which code letters cover your hazard and which combination of fabric and cut goes with it.
Last updated: July 2026