# Impact of Carpets on Indoor Air Quality
## 3 Effects of Carpets on IAQ
#### 3.1.1. Emission of VOCs with Carpets
The emission rate may be limited by one or both mechanisms based on the type of building material. In the case of the second mechanism (evaporation), the emission rate of VOCs may be affected by the concentration in the indoor air (equilibrium concentration) [41]. Additionally, the molecular weight of VOCs affects the emission rate as the diffusion coefficient mostly decreases as the molecular weight of the VOCs increases [42]. There are several models available for predicting VOC and SVOC emissions from carpets, such as the first-order decay and dilution models with or without considering the sink effect [42; 43; 44]. If the sink effect is considered in the model, a better fit between the predictor variable and the response was found, resulting in higher regression values [44]. However, a more rigorous validation of models is desirable because of the principal assumptions of the model effect on the predicted result of the model. For example, the result of separated fibres and polymer backings of the carpet confirmed that the backing was the most predominant source of emission due to serving as a slow diffusive source of the VOCs. Therefore, the model of these results assumed that the VOCs initiate emission predominantly from a uniform slab of polymer backing material; hence, the researchers claim that this model can predict VOC emissions from new carpets based solely on a knowledge of the physical properties of the relevant compounds and the carpet backing material [42]. Effect of ventilation: Both emission and evaporation mechanisms control the emission rates when the ventilation rate changes. Indeed, a significant impact of the ventilation rate on emission rates was achieved when the ventilation rate was low, but the emission rates become independent of ventilation rates when the ventilation rate is high in both sensory and chemical assessments [45]. For example, [PERSON] [45] studied the emission from construction products and found that when the low ventilation rate was increased (less than one week), the emission concentration of VOCs from the sources with large surfaces increased. This increase may be caused by an increase in the air velocity above the surface, increasing the mass transfer coefficient and consequently increasing the evaporation of VOCs from the surface [41; 45; 46; 47]. Effect of temperature: Generally, indoor air temperatures are limited between 17 \({}^{\circ}\)C and 28 \({}^{\circ}\)C. However, the temperature of the floor covering materials may increase to a higher degree by solar irradiation or floor heating. The VOC emission increases with higher indoor temperatures due to increased diffusion and evaporation of VOC from the surface. For example, the 4-PCH emission from carpets increased when the temperature increased from 23 \({}^{\circ}\)C to 50 \({}^{\circ}\)C [43; 48]. However, increasing the temperature decreases the amount of chemical compounds in carpets as well as the emission rate over time [47; 48; 49]. The emission of four finishing materials (carpet, oil-based paint, plywood board, and water-based paint) showed that different air temperatures (23 \({}^{\circ}\)C and 30 \({}^{\circ}\)C) significantly impacted the chemical emissions, but mainly for the initial emission. For example, after ventilation for two weeks, both the chemical (TVOC) and the sensory emission rate for each material showed no changes in emission between the two temperature levels [50]. Effect of dimensions of a space: Small chambers are typically used to study the influence of different parameters (e.g., temperature, humidity, air exchange rate, air velocity) on emission/sink properties of building materials [51], because in large chambers, the environmental conditions are difficult to control. Additionally, large chambers are cost-intensive, time-consuming, and require complicated test equipment [52]. However, large chambers are more practical in estimating real-life situations for simulating inhabitants' behaviour and sink effects of building materials [51].