Two Different Properties
Flame retardant describes how a material behaves when exposed to fire. It resists ignition and self extinguishes when the ignition source is removed. The measure most commonly quoted is oxygen index and a value of 25 or above is normal for a flame retardant polyolefin.
Halogen free describes what the material releases when it does burn. A halogen free compound contains no chlorine bromine fluorine or iodine so combustion produces no corrosive hydrogen halide gas.
A material can be one without the other. Many highly flame retardant compounds achieve their performance precisely by using halogenated additives.
Which Environments Require Which
| Environment | Usual Requirement | Our Grade |
|---|---|---|
| Tunnels metro stations | Halogen free | S3(n) S3(nh) S1(n)-10 S1(n)-35 T1 |
| Data centres hospitals | Halogen free | S3(n) S1(n)-10 S1(n)-35 |
| Vessels and offshore platforms | Flame retardant | S3 S3(h) S1-10 S1-35 |
| Shipyards and harbours | Flame retardant | S3 S3(h) |
| Buried and duct on land | Either — mechanical is the driver | S3(nh) or S3(h) |
Why Enclosed Routes Specify Halogen Free
The danger in an enclosed cable route is rarely the fire itself. It is the smoke. Hydrogen chloride released by a burning halogenated compound is acutely toxic to people evacuating and it corrodes electronic equipment far beyond the area the fire actually reached.
That is why metro tunnels data halls and hospitals specify halogen free and why the specification is usually non negotiable.
Why Marine Rules Specify Flame Retardant
On a vessel the priority is stopping fire propagating along a cable route through a steel structure where evacuation options are limited. Classification society rules therefore concentrate on ignition resistance and flame spread.
Our flame retardant grades are also formulated for wet and salt laden service which is a separate requirement that matters just as much offshore.
Reading a Specification Correctly
If a specification says low smoke zero halogen or LSZH it means halogen free. If it says flame retardant or references an oxygen index it means flame retardant. If it says both, tell us and we will confirm which of our grades satisfies both requirements for your position.
- Halogen free grades — S3(n) S3(nh) S1(n)-10 S1(n)-35 T1 C101 C105 C106 C107
- Flame retardant grades — S3 S3(h) S1-10 S1-35 S1
