Een stukje uit het boek "Toxicity of fire retardants in relation to life safety"
Smouldering/non-flaming fires
These involve slow thermal decomposition without flames, so that a serious hazard inside a building requires several hours to develop.The decomposition may be induced by heat supplied externally or may be self-sustaining. Slow thermal decomposition results in oxidative non-flaming conditions. The products are very rich in organic compounds (approximately 50% or the mass decomposed), which are usually highly irritant to the respiratory tract. Inorganic acids provide a further source of irritants. Another major toxic product is carbon monoxide. Such fires are usually small and develop slowly. They can present a serious toxic hazard over a period of an hour or more due to the slow build-up of carbon monoxide and organic irritants. Inorganic acid gases may also be released slowly if the appropriate anions are present in the material. In general, the toxicity of fire retarded materials would not be expected to differ greatly from non-fire retarded equivalents under these conditions. The presence of flame retardants may have a considerable influence on the probability that a transition to flaming combustion will occur, which may have profound effects on subsequent fire hazards.
Well ventilated flaming fires
These fires occur when there is plenty of air available so that the ratio of fuel to air is low. Under these conditions combustion is most efficient, so that for most non-fire retarded materials, the main products are carbon dioxide, water and heat and the yields of smoke and toxic products tend to be low initially. The toxic potency and toxic hazards from simple CHOcontaining polymers are therefore small to start with, but the fire is likely to grow quickly, producing considerable quantities of heat and carbon dioxide while consuming oxygen. The behaviour of fire-retarded materials during this phase of a fire depends to some extent on the nature of the fire, the materials being burned and the mechanism of flame retardancy. Fire retardants tend to act either mainly in the gas phase, by inhibiting flame reactions, or in the solid phase, by inhibiting combustion. Once the degree of ignition resistance afforded by the FR-treatment bas been overcome, then the fire retarded material will decompose in the flaming mode.
As the fire develops a more hazardous mixture of products may be formed. Carbon monoxide and carbon dioxide can be significant toxic products, and many inorganic products may be released as acid gases. Some materials (particularly if treated with fire retardants) are unable to burn efficiently, producing high yields of CO and organic products, particularly those treated with fire retardants acting in the gas phase. The early stages of most fires in buildings and fires outside tend to fit into this category. Such fires inside buildings are usually too small to present a significant environmental hazard outside the building, but may grow into post-flashover ventilation controlled fires.
