Gas absorption – a process when separate gas (vapor) mixes components are captured by the entire volume of sorbent liquid (or less frequently – a solid) creating a solution. Absorption is underpinning the technology used for extracting water vapors, hydrocarbon components and sulfur compounds from natural and synthetic gases, for treating gas discharges to protect the environment.

There may be chemical and physical absorption. Chemical absorption is a process when the absorbed component is bonded in the liquid phase as a chemical compound; practically complete absorption is possible. Physical absorption is a process when gas dilution is not accompanied by a chemical reaction; the component is absorbed until its partial pressure (a separate component pressure in the gas mix) becomes higher than the equilibrium pressure of the solution.

Absorption is a selective and a reversible process. The reverse process when the dissolved gas is recovered from the solution is called desorption. Combination of desorption and absorption allows for multiple reuse of the absorbent and for separating pure absorbing components. Absorption increases with pressure increase and temperature decrease. In coal mines, the rate of methane absorption by coal defines the level of gas content.