Just half the sunlight shines down through a ceiling of trees in a cloudy day in the forest.
Walking through forest with trees and tree roots acting as natural air filters to absorb the impurities, the air is fresher. Even the damp soil by a stream smells sweet, earthy. i think of the roots and fallen leaves layered through the soil, filtering everything and eliminating impurities for the earth.
Enjoy you walk in the forest or a garden.