In gas scrubbing, a distinction is made between physical absorption and chemical absorption.

In physical absorption, a substance or component is condensed in another component. This process is reversible, can’t be increased infinitely and depends on temperature, pressure and other factors.

Example: Methanol + water

A simple definition of chemical absorption is when a substance or component is often irreversibly chemically bound to another component or reacts chemically with it.

Example: Hydrochloric acid (HCl) reacts with caustic soda NaOH to form sodium chloride (common salt) NaCl and water H₂O: HCl + NaOH à NaCl + H₂O

Gas scrubbers (jet scrubbers and columns) are used for absorption.