Air contains oxygen, nitrogen, inert gases, CO₂, and water vapor.

The effects of air on mineral floatability are as follows:

(1) When a mineral breaks and exposes a fresh surface, it undergoes hydration upon contact with water, exhibiting hydrophilicity. However, when gas is adsorbed onto the mineral surface, it weakens the hydration process, creating initial hydrophobicity.

(2) The interaction between gas and mineral surface is selective; oxygen has a greater impact on the mineral surface.

(3) Oxygen is beneficial for the initial hydrophobicity of sulfide minerals. However, if the interaction time is too long, the mineral surface will revert to hydrophilicity. When gas adsorption conditions are appropriate, it can create hydrophobicity on the mineral surface, even allowing flotation without flotation agents (e.g., dry coal powder). Galena also requires the initial action of oxygen to react with xanthate and float.