Even though rubber is not a good food source for mold, if dirt/dust gets trapped in the mat and the conditions are right, it is possible. If this happens, bleach water and Sun Light should fix the issue in a few hours. Also, if mold starts to form, spray bleach water on the surface and the mold will start to die within 2-4 hours. We recommend mixing a spray bottle with 1/3 bleach and 2/3 water, spray the molded surface, and then expose the surface to direct sunlight. Playground swing mats are the largest playground mats that we have. The mat would get warm, depending on how much direct sunlight it receives. We always recommend wearing foot protection/footwear no matter what the outside play surface or temperature is.