Propagation and Diffusion of Fluorescent Substances with Footprints in Indoor Environments

Some studies have shown that contaminants can be transferred between floors and the soles, and there are few studies on pollutant propagation caused by human walking in real-life situations. This study explored the propagation and diffusion law of ground pollutants from rubber soles to poly vinyl chloride (PVC) floor during indoor walking through employing a fluorescent solution as a simulant. The footprint decay ( D ) and transfer efficiency ( τ ) of the fluorescent solution transferred from the sole to the indoor floor during walking were analyzed based on the fluorescent footprint imaging. The effects of namely body weight (50–75 kg), walking frequency (80–120 steps/min), and solution viscosity (oil and water) were also investigated. It was found that the total fluorescence gray value on the ground decreased exponentially as the number of walking steps ( i ) increased. The relationship between the normalized gray value of the fluorescent solution ( D ) on each floor panel i was D i = a e b i , 2.1 ≤ a ≤ 3.8 , – 1.4 ≤ b ≤ – 0.7 , and τ was distributed in the range of 0.51–0.72. All influencing factors had a significant effect on a , and a greater body weight resulted in a smaller a value, while only the body weight had a significant effect on b and τ , and a greater body weight led to larger b and lower τ values.