The bottom line is that unpleasant odors are quickly eliminated at the source. To understand properly the uniqueness of this concept, one must first look at the manner by which odors are perceived by us and at the physics and chemistry of odor production. Odor Perception Odor perception occurs when airborne gaseous molecules contact membranes in the nasal passage, which are rich in odor receptors. However, solids and liquids do produce gases which we perceive as odors. Odor Physics and Chemistry Liquids evaporate, or turn into gaseous molecules.
Mothballs are a common example of a solid which sublimes into gaseous, odor- producing molecules.
Increases in molecular activity can come about in several ways. Increased temperature can cause evaporation, as with boiling water. A more subtle example is human perspiration which is helped to evaporate by our body temperature. Changes in atmospheric pressure or exposure to atmosphere can also assist evaporation. Until perspiration reaches the surface of our skin it has nowhere to go.