## 2 Volatiles in Heritage Environments
### Volatiles Emitted from Heritage Objects
**Wax** is not an extensively studied material in terms of identifying the main volatile emissions in the cultural heritage field, but a strong resinous and waxy odour has been detected in association with wax sculptures stored in display cases [5]. SPME analyses identified 40 compounds such as alkylbenzene derivatives, naphthalene derivatives, n-alkanes, alcohols, n-alehydes, n-carboxylic acids, benzene derivatives, cinnamic derivatives and monoterpenes. Among these, the most important categories identified as markers for bees wax are n-carboxylic acids with 6-12 carbon atoms, n-alkanes, benzene and cinnamic derivatives. Some of the compounds detected are similar to those found in paper and wood analysis, such as furfural, vanillin and various benzene and cinnamic derivatives [5]. The predominant ones are benzenemethanol, cinnamaldehyde and benzoic acid, compounds defining the typical strong odour of beeswax [5]. Museum collections may also include **medicines, drugs, pharmaceutical products and perfumed products** (perfumes). These are characterized by both inorganic and organic volatile emissions. In a systematic study at the Smithsonian Institution's National Museum of American History, the most important volatile organic emissions from pharmaceutical products and cosmetics were analysed [2]. When analysing fragrances, cosmetics and disinfectants, most aroma compounds of plant or animal origin are terpene derivatives: camphene, \(\alpha\)-pinene, thujene, phellandrene, terpinene, limonene, terpineol, menthone derivatives, 3-carene and 4-carene. Most of them are strong-smelling compounds such as limonene--which is also often used in cleaning products--with a citrus odour, the isomers 3-carene and 4-carene, which are known for a sweet and pungent smell, and others that smell of resin, rosemary, herbs and wood [2]. Similar is the analysis of medicinal compounds: the most important compounds identified are thymol, isopropyl alcohol, eucalypt, methyl salicylate, menthol, paralledehyde, 2-propanol, 1,1,1-trichloro-2-methyl-, tribromomethane, acetophenone, trans-Z-\(\alpha\)-bisabolene, phenol and camphor [2]. These compounds are characterized by a distinct odour of herbs, wood, citrus, freshness and mint. In museums, galleries and archives, objects are usually stored in containers such as display cases, storage boxes and cabinets. This affects the indoor air quality, as the material of the enclosures can emit additional volatile substances. In addition, low ventilation or a lack of air exchange in the microenvironment leads to the accumulation of substances generated in the box [6; 32]. When different materials are present in the same environment, the volatile organic compounds emitted by an object can affect the behaviour of others. The damage can be caused by direct contact, i.e., when an object consists of several materials, or by indirect contact, i.e., when volatile organic compounds are transferred to the object through the air [23; 29]. Emissions from display case materials, such as VOCs from plastic, adhesive, rubber and wood components, and their effects have been studied [23; 33]. Wood is often chosen for display cases because of its availability and relatively low cost, but it is a precarious material that affects very different types of objects [34]. Oak is well known as a material emitting high content of acetic acid; therefore, its use is usually avoided in museums [35]. Carpeting materials nowadays include synthetic fibres such as nylon, olefin and polyester and natural ones such as wool fibres [36]. Wool and other proteinaceous materials may emit hydrogen sulfide [6] and thus represent a risk. Carpeting contributes significantly to the total VOC concentration indoors due to the large surface area [37]; on the other hand, they can also absorb and re-emit volatiles [37].