The International Sanitary Supply Association reports that most of the dirt that is present in a building comes from:

Question

Quizplus · Accepted Answer

People's shoes are the most common source of dirt in a building. As people walk in and out of a building, they bring in dirt, dust, and debris on the soles of their shoes, which then spreads throughout the building. The other options may contribute to the amount of dirt in a building, but they are not the primary source.

The International Sanitary Supply Association Reports That Most of the Dirt