Have you ever considered what your windows and doors may cause, during a fire?
To the opposite of all our wishes, fires happen each year, but these fires seldom destoy an entire building. These fires usually do not extend beyond the limits of severall small rooms or flats. In this case, the building may be re-used with some repair, ofcourse if poisonous and corrosive gases did not penetrate each corner. Actually the bulk of damage a fire causes, consists of the ones called the "secondary damages" happening after fire. Wood windows get burned, but much slowly when compared to other materials. They resist to burning usually more than 90 minutes and they keep most of their static strength during this time. In case of a fire, wood only gets carbonized on the surface and the stability is kept for a long time. Besides, it causes some amount of gas and smoke, whereas PVC releases very poisonous gases and looses its stability almost immediately.
Inorganic materials such as steel have important disadvantages in terms of fire even though they are fireproof. Steel which acts as a frame in structures looses its physical properties with rising temperature and causes all structure to collapse by becoming unable to carry the load. Wood, on the other hand, does not expand with temperature and dries with the effect of heat until burning point and gets even stronger.
Wood starts burning by itself only when its temperature reaches 330 to 520 oC. Outer surface transforms into charcoal while burning, which is a good insulator against heat. Because of the high insulation properties of wood itself as well as charcoal, it is very hard to bring the inner surfaces of a wood part to burning temperature. Therefore, as we all know, it is hard to burn big wood masses in fireplaces and barbecues. This is the case with sufficiently large profiles burning slowly.
Besides all these considerations, wood is ofcourse a burning material. None the less, burning products should be compared to other burning materials. During burning wood, water and carbon dioxide come out and these are not poisonous within reasonable limits. Wood has an important advantage when compared to other burning materials. It contains 8% to 15% water. For one ton of wood to be burned, 80 to 150 kg of water should be vaporized. When a wooden beam starts to be burned from four sides, the speed of burning inwards is typically around 0.5 mm per minute and the temperature of the non-burning part never exceeds 100 oC. The reason for this is the high insulation value of charcoal, wood and the water in the latter. Therefore, the remaining part keeps its stability for a long time.
In contrast to wood for which no additives are used during production, fluorine, chlorine and bromine is added into PVC in order to reduce its flaming properties. At 300 oC temperature, after 15 minutes, 80% of chlorine comes out as hydrochloric gas. This gas disintegrates easily with fire fighting water or water vapor in the air and forms hydrochloric acid. 250 grams of hydrochloric compound comes out from only 1 kg of PVC. This acid continues to get produced on and on with water vapor in the air even after the fire and creates a cycle. Hydrochloric acid drops fall down after the fire and starts damaging the surroundings. Even after months from the fire, corrosion is observed in every kind of equipment including electronics. People subject to this smoke suffer from permanent damage in the pulmonary tissue and eyes.
The biggest poison coming out when a PVC window is burned is the fatal Dioxin. It is almost impossible to restore an environment damaged by dioxin and hydrochloric acid. In U.S.A., annually 1 million incidents of fire in the average cause formation of Dioxin gas because of PVC products in the environment. Dioxin represents 210 different polychloric dibenzoidoxide and furan. These very poisonous materials come out by burning chloro-organic materials such as PVC. Dioxins cause cancer and damage immune system and liver and make changes on chromosomes. Therefore, 80% of deaths in fires are caused by smoke poisoning.
Even a small amount of PVC combustion fills a room with an intense smoke. This limits the chances of victims to escape. The effects of PVC in case of a fire are assessed by insurance companies. Therefore, many companies state that PVC should not be used in residences and work places. When it comes to wood windows, there are no additives with fire risks. PVC, as a chlorine product, is a product from the poison kitchen as defined by Greenpeace.
Waste of combustible PVC products is another environmental problem. There are heavy procedures in developed countries in order to eliminate unwanted situations.
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