the performance of optoelectronics by absorbing or scattering the light beams. Corrosivity of smoke produced by materials is characterized by the corrosion index (CI), defined as material loss rate (angstrom/minute) per amount of material gasified products (grams) per volume of air (m3). It is measured by exposing strips of metal to flow of combustion products in a test tunnel. Polymers containing halogen and hydrogen (polyvinyl chloride, polyolefins with halogenated additives, etc.) have the highest CI as the corrosive acids are formed directly with water produced by the combustion, polymers containing halogen only (e.g. polytetrafluoroethylene) have lower CI as the formation of acid is limited to reactions with airborne humidity, and halogen-free materials (polyolefins, wood) have the lowest CI. However, some halogen-free materials can also release significant amount of corrosive products. Smoke damage to electronic equipment can be significantly more extensive than the fire itself. Cable fires are of special concern; low smoke zero halogen materials are preferable for cable insulation. When smoke comes into contact with the surface of any substance or structure, the chemicals contained in it are transferred to it. The corrosive properties of the chemicals cause the substance or structure to decompose at a rapid rate. Certain materials or structures absorb these chemicals, which is why clothing, unsealed surfaces, potable water, piping, wood, etc., are replaced in most cases of structural fires. Health effects of wood smoke Wood smoke is a major source of air pollution, especially particulate pollution,pollution by polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) such as formaldehyde. In the United Kingdom domestic combustion, especially for industrial uses, is the largest single source of PM2.5 annually. In some towns and cities in New South Wales, wood smoke may be responsible for 60% of fine particle air pollution in the winter. A year-long sampling campaign in Athens, Greece found a third (31%) of PAH urban air pollution to be caused by wood-burning, roughly as much as that of diesel and oil (33%) and gasoline (29%). It also found that wood-burning is responsible for nearly half (43%) of annual PAH lung cancer-risk compared to the other sources and that wintertime PAH levels were 7 times higher than in other seasons, presumably due to an increased use of fireplaces and heaters. The largest exposure events are periods during the winter with reduced atmospheric dispersion to dilute the accumulated pollution , in particular due to the low