Indoor chemical reactions

Exothermic chemical reactions Endothermic processes pressure Material handling and transfer Enclosed or indoor process units Access relief pressure Drainage and spill control Toxic materials Sub-atmospheric Operation in or near flammable range Dust explosion... 

Weschler, C.J. (2004) Chemical reactions among indoor pollutants what we ve learned in the new millennium. Indoor Air, 17 (Suppl. 7), 184-94. 

Generally the indoor environment allows different chemical transformation reactions to occur than usually predominate in the outside atmosphere. So called night-time chemistry (atmospheric chemical reactions not driven by photochemistry) is usually a good starting point to consider the in-museum chemistry that goes on. 

Most classes of VOCs found in indoor environments are sampled onto sorbents by adsorption but highly reactive VOCs like carbonyl compounds are sampled by chemical reactions with the sorbent. Thus aldehydes and ketones are sampled by their reactions with sorbent gels coated with 2,4-dinitro-phenylhydrazine to form stable hydrazones [38-40]. Similarly, formaldehyde has been sampled by its reaction with N-benzylethanolamine to give 3-benzyl-oxazolidine [41,42]. 

During the manufacturing process of styrene-butadiene rubber the polymerisation is stopped at a conversion rate of less than 90%. The residual monomers styrene and butadiene are removed by distillation. The odour-in-tensive compounds 4-phenylcyclohexene (from styrene and cis-butadiene) and 4-vinyl cyclohexene (from cis-butadiene and trans-butadiene) can be formed from the remaining monomers under the conditions of a thermally permitted Ti2s-t- 4s Diels-Alder cyclic addition. During indoor air measurements, carried out in six different office rooms in each case 3 days after new carpets had been laid, concentrations of 4-phenylcyclohexene of 29-45 pg m could be ascertained. It is suspected that the emission of the trimer of 2-methyl-l-propene from a glued carpet is also caused by chemical reaction. 

Several questions arise. How did these trihalomethanes get into the pool and why are they a problem in indoor pools THMs are products of chemical reactions between the chlorine used to disinfect the pool and organic substances from the swimmers themselves. Skin cells are shed into the pool, along with lotions and other body care products. Organic molecules from these substances are chlorinated to produce the trihalomethanes. THMs are volatile compounds. In an outdoor pool, they would evaporate and be blown away by the breeze. In an indoor pool, where there is less air circulation, THMs tend to build to higher concentrations in the air above the pool. These fumes are inhaled by the swimmers and the THMs diffuse into the blood. 

The conditioning and control of indoor environments is an ever increasing problem. Lately this does not only include the traditional control of temperature and moisture but also the elimination of contaminants and odors from the atmosphere. Particulates, including organic matter, such as mold, germs, and viruses, can be captured and retained by sometimes electrically assisted ultrafiltration. Cartridges are either discarded or cleaned/reactivated. For the elimination of chemicals and odors, absorption, adsorption, and chemical reactions with air purification media are required. 

Furthermore, chemical reactions between pollutants in indoor air has been paid increased attention over the last few years. When present in indoor air, for example, ozone... 

When studying chemical reactions in indoor air it can be of great value to obtain continuous data of a number of influencing parameters (Weschler and Shields, 1994). In addition to the concentration of the reactants indoors and outdoors, the real-time monitoring should preferably include also the air exchange rate, temperature and relative humidity. 

Secondary emission is any process that releases new airborne contaminants from existing sources, changes the total emittable mass of existing contaminants, or results in chemical reactions between compounds on surfaces and in the air. Secondary emission may be based on sorption, oxidation, hydrolysis, decomposition or other chemical reactions in or on a source or the indoor air. A secondary emission process is often highly influenced by past and present environmental conditions. It is not always possible to tell if a compound found in the air is there because of a primary or secondary emission process since a source may emit the same compound by both primary and secondary processes. Purposely added materials such as cleaning products may be a primary emission source, but reactions between constituents of new and existing products may cause a secondary emission process. 

The physico-chemical properties of radon and its decay products are presented in a series of reports primarily focusing on the decay products. However, Stein (1987) presents a review of his pioneering studies of radon chemistry and the reactions of radon with strong oxidizing agents. Although radon is not chemically active in indoor air, it is interesting to note that radon is not an "inert gas. 

Enviromnent and health-related problems Bio varnishes , i.e. varnishes based on natural, renewable raw materials, were developed as close-to-nature alternatives (substitutes) i.a. as a reaction to the so-called German wood preservative scandal and indoor pollution due to chemical solvents. Nevertheless, they have until now had a relatively high content of volatile bio-organic solvents, which may cause irritations, allergic and neurotoxic reactions, and contribute to the formation of tropospheric ozone. 

In order to meet the above-mentioned conditions and also to minimize dust entry, modern cases are predominantly highly sealed, which implies that the air exchange rate would be lowered to a minimum. It is to be assumed that the high surface to volume ratio, which especially characterizes smaller enclosures, combined with unsuitable construction materials and almost static conditions, enhance the accumulation of chemical compounds. Hence, the comparison of the indoor environment as a reaction vessel , as stated by Weschler and Shields (1997), comes to a head in museum showcases. 

A great deal of chemical transformation takes place before consumers receive their furniture, flooring, and other indoor building materials. Polymerization of glues, coatings and plashes, or heat processing of manufactured wood products, generates volatile by-products that can continue to be emitted from the material after it has been installed. Once installed, further transformations increase the load of odorous or toxic gas-phase species (Uhde and Salthammer, 2007). Reactions discussed here include oxidation and hydrolysis. 

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