# Impact of Carpets on Indoor Air Quality
## 4 Conclusions and Recommendations for Future Studies  
Carpets are one of the elements in buildings that cover a large floor area of indoor spaces and can have a major impact on indoor air quality (IAQ) because of their multiple layers of material and high surface area of dense fibre piles. This review seeks to summarize the current understanding of how carpet affects indoor volatile organic compound (VOC) concentrations and particulate matter (PM) distributions. The following main findings can be concluded:  
* In real situations, the effects of carpets on IAQ are complicated because carpets affect the emission, sink, and transformation of VOCs. Previous studies showed that each layer of a carpet (fibre pile, backing, and adhesive) influences these behaviours. * Carpets with separated layers showed that VOC emissions from the complete structures were lower than the sum of emissions from the single component layer, while \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Ref** & **Test Materials** & **Test Chamber** & **PM Type** & **RH** & **Resuspension Rate** & **Major Results about RH** \\ \hline \multirow{4}{*}{[81]} & \(\bullet\) & New and old & Full-scale & ISO 12103–1 Test & & & \(\bullet\) & The individual \\  & & level-loop carpets & experimental & ISO 12103–1 Test & & & & variability of \\  & \(\bullet\) & Vinyl tile & chamber (4.88 \(\times\) 3.05 m) & dust (A1) & 30–50\% & \(1.7\times 10^{-7}\)–1.7 \(\times\) & simulated walking \\  & & & \(3.66\times 3.05\) m) & (0.8–10 \(\mu\)m) & & & \(10^{-4}\) min\({}^{-1}\) & & outweighed the effect \\ \hline \multirow{4}{*}{[90]} & \(\bullet\) & Medium-pile dirty & & & & & \(\bullet\) & High RH enhanced \\  & & carpet (8 mm & nylon fibre) & Chamber & ISO 12103–1 Test & & & \(5.0\times 10^{-6}\)–4.0 \(\times\) \\  & \(\bullet\) & Medium-pile clean & (7.0 \(\times\) 4.0 \(\times\) & dust (A1) & & & \(10^{-2}\) mg/mg \\  & & carpet (10 mm & 6.5 m) & (0.8–10 \(\mu\)m) & & & (Emission Factor) & the opposite effect \\  & & nylon fibre) & & & & & & with old carpets. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Effect of humidity on particle resuspension from carpets in previous experiments. the sorption was possibly higher due to the differences in the geometric configurations of the fibre. * Carpets work as sorption sites with the ability to reduce peak concentrations of indoor VOCs and re-emit them over prolonged periods. Indoor environmental parameters such as RH affect the carpets' sorption capacity of VOCs depending on the molecules' hydrophilicity or hydrophobicity. * In general, carpets resuspend more particles than hard floorings, and bigger PMs resuspend from carpets more than smaller PMs through human activities. In addition, the effects of RH on PM resuspension depend on the surface conditions of carpets, particle size, and particle types (hydrophilic or hydrophobic). While the impact of the carpets on IAQ is well documented in laboratory studies, the effect of carpets on indoor air in real-life settings like living spaces and workplaces requires further investigations to clarify the full capacity of carpets. To better understand how carpets influence VOCs concentrations in actual indoor environments, future studies are needed to evaluate the carpets' sorption capacity of VOCs emitted from different building materials or human activities and measure re-emissions over long times. This risk and benefit of carpets on the sorption of VOCs demonstrates the effects of carpets on IAQ. For example, VOCs can be absorbed when a source is present and be re-emitted when the source is gone; or absorbed when windows are closed (no ventilation) and desorbed when windows are opened, in the case of a permanent source. In addition, more studies are needed to clarify the proportion of each layer in carpets' behaviour regarding IAQ. The results of these experiments could lead to more knowledge on the material needed for each layer to improve the positive impact of carpets on IAQ.