According to the ISSA, 15 feet of entrance matting can prevent 80- 90% of the dirt that is tracked in by foot traffic. Typically, this rule of thumb of 15 feet of matting is achieved through a 3-mat system of three 3'x 5' mats. The main function of entrance mats is to remove the elements off shoes to prevent dirt, dust, and moisture from being spread throughout your facility.