The harmful effects of oxidation on metals from hydrochloric acid caused as a result of a fire are known to all those who work because, in almost all cases, Bobbio turn to for specialized firms' performing the necessary remediation. Tutavia this issue is less known regarding the effects on historic buildings and their priceless contents.
Prysmian, a spinoff company formed by Pirelli and a global leader in the production and laying of electrical cables, has carried out a study on this issue by comparing the emissions of a traditional cable with a type of low-emission Afumex. The study is particularly interesting, was presented with an article of which we give the full text:
Presence of cables inside historic buildings
The use of cables inside the historic buildings is very different and may be present plants of various kinds, and these cables take up a considerable mass, and in case of fire emissions from their combustion activities exert a pernicious role, not only on architectural surfaces, but also on the materials from which objects belonging to museum collections are often housed in the interior concerned (metals, painted surfaces, wood, paper, ivory, ceramics, glass, etc..) The importance of having available a technology advantage in terms of very low emission of harmful gases, it is evident. The problem was well known from past centuries: an English chronicler of the seventeenth century, John Evelyn, noted the presence of yellowish or dark brown patina that were forming in those days, the paintings of what constituted the core of the National Gallery London, and then it was already stored in the city center. He attributes the formation of such coatings to the filing of smoke from combustion, made for home heating and craft activities. In those days, was thus already aware of the possible damage caused by the toxicity to humans, but also damage to the surfaces of artifacts. In this case, the type of combustion were not accidental, but were due to human activities, and were aggravated by the fact that in England they used to burn coal, whose emissions, particularly given the compositional nature, are most degraded than those of wood . It is well known that in the fumes can be identified: •
anhydrides of sulfur oxides of nitrogen
• • •
hydrochloric acid, hydrofluoric acid
• unburned particles.
The first terms in this series are able to give pH acid solutions (either directly or as a result of hydration) and therefore engaged in degrading and corrosive action, they usually take place when they go to burning plastic materials contained in the interior of a traditional cable. Then there are molecules, such as carbon dioxide, which does not exert a direct chemical on art materials, but are able to carry out a specific degraded against the plaster and stone-type carbonate. The particles consist of the fumes and soot particulates are responsible for the deposits of blacks and yellow glaze which we have referred and color variations that are essential in terms of "readability" of the surface, these deposits are to be considered in terms of conservation of the area, as they contain some chemicals that are capable of accelerating the degradation of underlying materials. The research carried out examined the fire behavior of cables of different construction types, and evaluated the emissions take place during the combustion of traditional cable (or standard) and during the burning of cables with low emission type Afumex. In the case of hydrochloric acid, the gas evolved in very significant quantities in the burning of cables whose insulation is made from compounds based on PVC (polyvinyl chloride), there was resounding difference in comparison with a cable of Afumex that do not contain halogen in the compound, did not play any emission of hydrochloric acid. We have detected a trend in emissions, basically similar to that of hydrochloric acid, also with regard to carbon dioxide. Assessing the progress of the graphs, we note that the cable type Afumex, not only the emission is significantly lower than that in standard cables, but the emission peak is reached in a time about twice as compared to traditional systems. Of course, this does not really matter as far as the art work, but it is very important to enable the safe evacuation, of any local interest in combustion, from visitors and staff.
Read more: http://www.prysmian.it/export/sites/prysmian-itIT/attach/pdf/Afumex_Guida_all_Uso.pdf
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