Here a quote that attempts to explain the situation Quote: Most of the elements used in the spray are heavier than air, even in their powdered form they are heavier and will sink quickly. Mixing them with the polymers suspends the particles in the atmosphere high above the surface for longer periods of time, therefore in theory we do not need to spray as often or as much material. Since the suspended particles eventually do settle into the lowest part of the atmosphere and are inhaled by all life forms on the surface there is an attempt to counter the growth of mold by adding to the mixture mold growth suppressants - some of which may be of biological material.