All you need to Know about the Topic of Fire Protection

GRP Fire Protection Lexicon

Fire Protection and the most Important Technical Terms used in that Context


Aluminium hydroxide (or aluminium tri-hydroxide Al(OH)3): a compound that breaks down into water at temperatures above 200°C. ATH thus cools the seat of a fire through evaporation and simultaneously prevents oxygen from reaching the flame. The solid residue from the release of water, aluminium oxide, also provides additional shielding of the seat of the fire.


A chemical element from the nitrogen group of the periodic table (symbol: Sb). Antimony compounds strengthen the flame-retardant effect of halogens. But many of them are toxic.


Deliberate “charring” of a surface: the thin carbon layer prevents the laminate components underneath it from coming into contact with oxygen.

EN 45545-2

The standard that regulates the requirements of the fire behaviour of materials and components in rail transport. As trains are difficult to evacuate (in a tunnel, for example) in the event of a fire, EN 45545-2 is extremely strict. Fire safety systems that meet its requirements must be very carefully designed and are regarded as the “gold standard” in many other areas of application.


A flame is much more than just a light phenomenon that accompanies fire, it is the essence of the fire itself. The flame is the area in which fierce, heat-generating chemical reactions take place between the oxygen in the air and the volatile components of a flammable material. If it is possible to prevent these reactions, the flame goes out and so does the fire.


Chemical elements in the 7th main group of the periodic system, such as chlorine (Cl) and bromine (Br). They can prevent the spread of flames in the air by disrupting the chemical reactions that contribute to the generation of heat in a flame.


Containing halogens. For flame retardants that contain chlorine or bromine.


Hazard Level. A classification system that helps to order the areas of application of (not only) plastic components according to the minimum performance required of them in a fire. The strict rail transport standard DIN EN 45545 has three hazard levels; the requirements of the strictest – HL3 – apply, for example, to sleeping cars in trains, for which evacuation is not possible via side access points within four minutes in the event of a fire.


Formation of a protective foam layer as a result of the effect of heat on a plastic. The protective foam prevents oxygen from penetrating and shields the laminate beneath it from the heat for a certain time. Intumescence is therefore an enhanced form of carbonisation.


Limiting Oxygen Index – an important indicator for describing the fire behaviour of plastics. The number indicates how much oxygen the material needs to ignite. Above an LOI of 21, a material is difficult to ignite in air. The higher the number, the greater the protection against fire offered by the material.


Chemical element that is widely used as a flame retardant. In the event of a fire, it draws water from the subsurface and forms phosphoric acids (which are not very caustic). This creates a protective layer which gases such as oxygen can only pass through with difficulty (see carbonisation).


Mixture of finely distributed droplets of liquid and dust particles created in a fire. Thick smoke can prevent visibility on escape routes, toxic smoke can harm people. Ideally, burning plastics only produce thin, non-toxic smoke thanks to carefully selected flame-retardant additives


The gas that drives the combustion processes. The air we breathe contains around 21% oxygen. Without this gas, a flame will go out.


The classic extinguishing agent. Water puts out flames because it cools down the seat of the fire and reduces the development of flammable gases from the burning material. It also prevents oxygen from reaching the seat of the fire and thus stops the heat-generating reactions in the flame. There are some flame retardants, such as ATH, that break down into water under the effect of heat.