# Impact of Carpets on Indoor Air Quality
## 3 Effects of Carpets on IAQ
### Particulate Matter
#### 3.2.2. Particulate Matter Resuspension from Carpets
In contrast, one study reported that a laminate floor resuspended more particles (5 \(\upmu\)m and 10 \(\upmu\)m) than carpets through vacuum cleaning after several times of simulated walking activities. This result may be related to the surface condition of the test carpets and the positions of embedded particles inside the carpets [79]. Humidity and PM resuspension. Table 1 summarizes the effect of humidity on particle resuspension from carpets in previous experiments. It lists the property of the test carpet, size of the test chamber, PM type, humidity levels, and measured particle resuspension rate. One experimental study showed that the resuspension rate of PM could be increased and decreased by higher RH depending on the surface condition of the medium-pile carpets (old and new) [90]. Another study showed that increased RH levels (40% and 70%) enhanced dust resuspension from nylon high-density pile carpets, while hard floorings showed decreased resuspension [89]. It is also reported that shaggy carpets did not show an obvious influence of different RH (40, 60, and 80%) on the mass concentration of particles with diameters between 0 and 5.0 \(\upmu\)m but showed an influence on the mass concentration of particles with diameters between 5.0 and 10.0 \(\upmu\)m [91]. This result may be affected by condensing of fine particles due to humidity. The RH levels affect the electrostatic and capillary forces of particles. In high humidity conditions, the capillary force will be increased by forming meniscus between particles and surface asperities, and the adhesion force will be increased. Additionally, higher RH increases cohesive forces between the particles and helps to form an agglomerate, resulting in the reducing resuspension due to the presence and strength of the particle clusters [89]. Moreover, the adhesion force by electrostatics was thought to decrease with higher RH because the extra water increases the leak-off rates of charges on particles, resulting in a reduction of adhesion forces and prevention of charge accumulation [89]. However, the results of [PERSON] et al. [89] showed that the difference in surface materials caused differences in the impacts of the capillary and electrostatic forces on particles' adhesion forces in the different RH conditions. Thus, the effect of RH on PM resuspension can differ depending on the material type and surface condition of carpets. The previous studies also showed that the effect of indoor RH on the resuspension of PM from carpets is related to the type of particles. A recent study examined the effect of humidity on the resuspension of biological particles from nylon carpets and linoleum [88]. While hydrophilic particles (quartz and dust mite) showed an increased resuspension rate as RH decreased from 80% to 10%, the resuspension rate of hydrophobic particles (cat and dog fur) did not show a significant effect of RH. The hydrophilic particles may make water films under high humidity conditions by absorbing moisture. The water film may reduce particles' resuspension by increasing the particles' adhesion force and decreasing the potential for electrostatic repulsion.