# Impact of Carpets on Indoor Air Quality
## 3 Effects of Carpets on IAQ
#### 3.1.1. Emission of VOCs with Carpets
Emission of the same carpets in various sizes of chambers with the same air temperature and humidity is ideally expected to demonstrate similar results. However, in some studies, significant differences in the emission isotherm of the carpets in a large chamber (30 m\({}^{3}\)) compared to small chambers (0.02, 0.28, and 0.45 m\({}^{3}\)) were found [4]. Effect of carpet materials: The material components of carpet layers affect the emission behaviour of carpets. Several studies have been performed on VOC emission of carpets with different material compositions, various fibre piles and backing, the same fibre pile and different backing, and even the same fibre pile and backing. In a study on VOCs emission of 14 carpets with separated layers, emissions from the complete structures were found to be lower than the sum of emissions from the single component layers [53]. A study on the emission from six carpet fibre materials (Triexta (polyester family made by polytrimethylene terephthalate, DuPont), Poly-triexta (75% Polyester, 25% Triexta), polypropylene (PP), polyester, nylon, and wool) showed that VOCs emissions varied significantly as a function of fibre type. Nylon and PP carpets showed the lowest and highest emission of carbonyls, respectively. Formaldehyde (an important harmful agent for human health) emission of Triexta and polyester carpet samples showed the lowest and highest emissions at 3 and 16 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\), respectively [54]. The VOC emission from carpets with the same fibre pile can be different when the backing of these carpets are different [53]. For instance, a polyamide carpet with a PVC backing emitted vinyl acetate, acetic acid, 2,2,4-trimethylpentane (isooctane), 2-ethyl-l-hexanol, and 1,2-propanediol (propylene glycol), while the dominant emitted compounds by a polyamide carpet with a polyurethane secondary backing were hexamethylcyclostrisiloxane, 1 butanol, dipropylene glycol methyl ethers (three isomers), and 2,6-di-terf-butyl-4-methylphenol (butyled hydroxytoluene or BHT) [44]. Therefore, it is clear that the carpet's backing affects the type of emitted VOCs [4; 42]. Indeed, the VOCs emitted from the backing of a carpet can occur for a long time, and even the air velocity cannot increase the emission rates because the diffusion of the VOCs from the carpet backing is the dominant process [41; 42]. For example, 4-PCH is a strong odorant originating from the SBR backing of a new carpet, and the emitted odour may continue for several months [44]. VOC emission from the same fibre pile and backing even disclosed different results. For example, polyamide carpet with SBR latex adhesive backing mainly emitted benzyl alcohol, toluene, and negligible amounts of siloxanes, aldehydes, and aromatics (like 4-PCH), without any emission of the base, acid, and formaldehyde [55], While in another study, it was reported that the primary emission of two polyamide carpets with SBR was styrene, 4-PCH, 4-ethenylcyclohex, and alkyl benzenes [44]. Further details from experiments and compositions of these carpets need to conclude why there are differences in VOCs emission with the same materials. For instance, it is unclear whether these carpets had the same adhesive glue, weight, and fibre pile thickness. Formaldehyde emission is expected to release unreacted formaldehyde from the adhesive glue for bonding the fibres and the backing of the carpet. One study showed that a wool carpet emitted more formaldehyde and TVOCs than a polyamide carpet and a mixture of wool/polyamide carpet. However, they reported that these results could have been attributed to the backing materials and/or adhesive glues of the carpets [4]. Effect of the preparation of carpet: The differences in VOC emissions varied among the same product types, which reveals apparent differences in manufacturing processes and ingredients [56]. In 1992, four independent variables were examined: oven residence time, latex amount (coating weight), makeup air feeding the drying oven, and type of SBR to produce carpet with low emission.