Fire Behavior

Even PVC products can catch fire. The following information provide a short overview about how PVC reacts in the event of fire.

If it Burns

Plastic materials and natural products can only catch fire if sufficiently large ignition sources and oxygen are available. In the process, aerosols and soot arise as well as gases which enflame and react to oxygen.

Fire Gases

The toxic properties of gases from burnt plastic materials are comparable to those which result from the burning of natural materials such as wood and paper. Numerous investigations have shown that approximately 90 – 95% of deaths during fires can be traced back to carbon monoxide (CO) poisoning. This gas arises during every fire and kills without warning. In contrast, hydrogen chloride (HCl) forces one to flee due to its pungent odour, even in the smallest, harmless concentrations.

pvc-kabel

Smoke Gases

There are numerous discussions about carcinogenic smoke gases besides the acute toxic fire gases (CO, HCN, acrolein, HCl, etc.). They also are produced by every fire. Some of the most important of this kind are PAHs (polycyclic aromatic hydrocarbons) and fine dust particles.
When materials containing chlorine such as PVC, or other plastic and natural substances, catch fire, dioxins and furans may result. These substances, however, bond strongly to the soot particles created during a fire and therefore are not bioavailable to people, animals, and plants. In examining people exposed to fire in contrast with those not exposed to fires, higher levels of dioxins could not be determined. The same conclusions were reached after PVC fires, e.g. in October 1992 in Lengerich/North Rhine-Westphalia, where several hundred tonnes of PVC went up in flames.

Corrosion

Every smoke gas is corrosive due to high temperatures, humidity, etc. If this gas contains additional acids (e.g. NOx, SOx, HCl, acetic acid), that can increase the effect. When PVC catches fire, a special corrosive smoke gas arises based on its chlorine content – HCl. Recent studies show that corrosion – contrary to the opinion of certain experts – in the case of fire does not play a role in the feared outage of safety electronics because it happens comparatively slowly over a long period of time. Important reasons for the outage of safety electronics are short circuits which result from electrically conducted soot residue.

The amount of economic damage due to corrosion depends on the circumstances of the fire and the beginning of the renovation work; it may increase if the renovation work takes place at a later date. In the process, the overall economic costs show that the economic advantages of using PVC are greater than the possible damage from a fire. The replacement costs alone for PVC cables in Germany would amount to approximately one billion euros per year. These costs are therefore similar to renovation costs (not only due to corrosion) for all fires in Germany (source: Engelmann: “Kosten-Nutzen-Abschätzung: Halogenfreie oder PVC-Kabel”, in: Vorbeugender Brandschutz, 1995).