# Impact of Carpets on Indoor Air Quality
## 3 Effects of Carpets on IAQ
### Particulate Matter
#### 3.2.2. Particulate Matter Resuspension from Carpets  
Previous experimental studies on particle resuspension from carpets mainly focused on the effects of human activities and indoor RH. Some studies compared the resuspension rate (fraction of a surface species removed per unit time) of particles from carpets to other flooring materials. Various scales of chambers were used in previous studies, and some experiments were conducted using human subjects to simulate resuspending particles by walking. The types of test particles were also different between the experiments, and dust samples from actual building carpets and ISO 12103-1 test dust (Arizona test dust [77]) were mainly used in the previous studies. Human activities and PM resuspension. The key reason for the resuspension of PM from carpets is human activities such as vacuum cleaning and walking [78; 79]. Previous studies showed that the size of PM affects the resuspension mass, and bigger PMs consistently resuspended from carpets more than smaller PMs through human activities. For example, one study showed that PM\({}_{10}\) has more resuspended than PM\({}_{2.5}\) during vacuum cleaning [80]. Additionally, the resuspension rate was higher for larger particles (size range of 0.8-10 \(\upmu\)m) during walking on loop fibre carpets [81]. Another full-scale chamber study using a walking subject also found a higher resuspension rate for bigger particles [82]. The dominant adhesion and removal forces of particles to carpets vary depending on their sizes. While adhesion forces increase with particle size, the removal forces, such as drag forces of vibration and convection, are proportional to the third and second power of the particle size, respectively [83; 84]. Therefore, larger particles more easily resuspend than smaller particles. Some recent studies focused on particle resuspension and exposure induced by infants' crawling and children's walking. A study that used a robotic infant showed that an infant would receive a nearly four times greater respiratory tract deposited dose of resuspended biological aerosol particles than an adult in terms of per kg body mass [85]. Additionally, the resuspension fractions for infants' crawling (10\({}^{-6}\)-10\({}^{-1}\) [-]) are similar to those for adults' walking [86]. Another study used a bipedal robot simulating children's walking and showed that different shoe materials (cotton socks, polyvinyl chloride, and ethylene-vinyl acetate copolymer) produced different sizes and concentrations of particles from carpets [87]. Flooring materials and PM resuspension. In several studies, the resuspension rate of PM between carpets and other hard flooring materials was compared. Generally, carpets resuspend more particles than hard floorings. A new level-loop carpet had a higher resuspension rate than vinyl tile flooring for particle sizes of 1.0-10 \(\upmu\)m via walking activityunder a ceiling air supply system [81]. Another study that used air jet tubes to simulate vortices induced at the edges of the foot during human walking also reported a higher resuspension rate from nylon carpets than the linoleum surfaces at the same RH levels (10% and 80%) [88]. In addition, the linoleum surface showed significant increases in the resuspension rate of hydrophilic particles as RH decreased from 80% to 10% compared to nylon carpets [88]. Another study that used a mechanical resuspension device to simulate human walking also showed higher resuspension fractions of nylon cut pile carpets than hard floorings (hardwood and vinyl) for particles 3.0-10 \(\upmu\)m [89]. In previous studies, it was found that the carpets' surface roughness, fibre resiliency, and electrostatic force may cause a higher resuspension rate of carpets [89]. In addition, low-density carpets resuspend dust more than high-density carpets because of the lower bending resiliency of fibre piles [89].