Labs are normally cleaned by contracted company and their employees use different methods to remove dirt from the floor. The worst method I've seen so far is by using broom to sweep up the dirt. The smaller particles are prone to linger around the air and subsequently land onto benches, bottles, and opened solutions. If you are plating on the same day the floor is swept, you will realize that the plates will get contaminated with fungi the next day (if you are lucky). That's how bad sweeping in the lab is.
The best way to prevent unsettling dust and contaminating the air in the lab is to use electrostatic fabric that will attract dusts and which can be subsequently disposed of.