# Impact of Carpets on Indoor Air Quality
## 3 Effects of Carpets on IAQ
#### 3.1.2 Sink Properties of Carpets for VOCs  
Research has shown that the sorption potential of carpets may have an impact on IAQ; sorption and desorption of VOCs on materials, are therefore, relevant to consider [57]. However, to test whether 100% of the adsorbed VOCs are re-emitted, long-term desorption data are required to monitor [58]. Carpet materials have been shown to have the largest sorption capacity among different indoor surface materials. Due to their ab/adsorption properties, carpets can reduce indoor air VOC concentrations, but has shown to be followed by re-emission of those VOCs over prolonged periods [59]. Effect of environmental parameters: It has been observed that RH significantly impacts the sorption amount of 2-propanol, a highly soluble VOC. However, no noticeable impact on sorption with increasing the RH was seen for nonpolar VOCs on polyamide and poly olefin carpets [59]. Therefore, it was concluded that RH affects the sorption capacity of VOCs based on the hydrophilicity or hydrophobicity of those VOCs. In a study, it was found that an increase in temperature and air velocity affected the amount of VOCs adsorbed by ceiling tiles and carpets [12]. In another study, the results of adsorption and desorption of some VOCs in the temperature range of 25-45 \({}^{\circ}\)C showed that the adsorption rate decreased more rapidly with increasing temperature than the desorption rate [3]. Additionally, some studies showed that the air velocity and size of chambers did not influence the sorption of VOCs on wool and nylon carpets [57; 60]. Moreover, the sink effect of the chamber test can influence the sorption study. To minimise this sink effect, the use of inert materials such as Teflon or glass for chamber walls has been recommended. In addition, results of wool and nylon carpets' sorption studies showed that an experiment conducted with a relatively high loading of VOCs liquid reduced the sink effects of the test chamber and is therefore recommended as well [61]. Effect of type of VOCs: A study on the sorption of toluene and a-pinene by wool and nylon carpets revealed that the sorption was enhanced when both compounds were present in the chamber. The outcome of the experiment was successfully used in the Langmuir model in order to provide a chemical explanation of the adsorption process [62]. Effect of carpet materials: In a study with two nylon carpets from different suppliers, similar sorption capacities were found while the emissions differed. Moreover, another carpet with mainly olefin-based fibres revealed a greater sorption capacity for all VOCs than these two nylon carpets [59]. A study on the sorption effect of carpets comprising of different materials resulted in the following ranking of the sorption capacity for toluene and \(\alpha\)-pinene: wool carpet > nylon carpet > PVC coverings > cotton curtain > empty chamber. Additionally, for the wool carpet, it was found that different air velocities (0, 10, and 20 cm/s) did not influence the sorption capacity because of the large surface area of the carpet [57]. Interestingly, carpet (fibres-backing composite) showed the highest sorption for all VOCs in comparison with the sorption capacity of the separated fibres and backing. In addition, this carpet revealed a higher sorption reaction than the sum of fibre + backing sorption, possibly due to the differences in the geometric configurations of the fibre [59]. From these results, it can be concluded that a carpet's structure can impact the carpet's sorption properties, and more studies are required to optimize the effect of the carpet's structure on sorption properties. As carpets are manufactured with various layers, one study considered the sorption of different VOCs on the fibre pile and backing [59]. The results showed that the polypropylene backing adsorbed significant amounts of VOCs, especially for o-dichlorobenzene and 1,2,4-tri-chlorobenzene, toluene, tetrachloroethene, and ethylbenzene.