In air stripping, contaminates dissolved in water are transferred to gaseous form by contact with relatively clean air, an example of mass transfer. Air stripping works best with volatile organic compounds (VOCs) and dissolved gases. VOCs are compounds with high vapor pressures, that is, compounds that tend to evaporate quickly. A common application of air stripping is the cleanup of groundwater contaminated by leaking fuel storage tanks. Air stripping is optimized by maximizing the surface area between the contaminated water and clean air, accomplished by creating fine water droplets in air or small air bubbles in water. Systems can be located away from the contamination (e.g., a system cleaning groundwater that is located on the earth's surface), or located within the contaminated zone (e.g., a system located in wells installed in contaminated groundwater). In some cases, the contaminated air from air stripping is released to the atmosphere, where the pollutants are destroyed by sunlight or reaction with other chemicals, adsorbed into soil or water, or diluted. Preferably, the organics in the exhaust from air stripping are destroyed by incineration or oxidation, or captured by adsorption.

The air stripping process may also be reversed. In air scrubbing, pollutants are transferred from contaminated air to clean water. However, a chemical reaction is often incorporated into air scrubbing, converting pollutants to a safer form. For example, sulfur dioxide produced during coal combustion can be removed from exhaust gas by mass transfer to water containing sodium hydroxide or carbonate, which converts the sulfur dioxide to calcium carbonate. Natural air stripping and air scrubbing also occur. Surface waters, such as lakes and oceans, serve as sinks for pollutants released to the atmosphere. Contaminated water left exposed to the atmosphere will release VOCs.

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