Many neutralisation reactions that take place in gas scrubbers are exothermic, i.e. have a positive enthalpy of reaction (also known as reaction heat). The heat released must be removed from the scrubbing cycle (e.g. with a heat exchanger) or compensated for by adding enough of the cold and fresh scrubbing medium.

Example: Hydrochloric acid (HCl) + caustic soda (NaOH) à common salt (NaCl) + water (H2O): released enthalpy of reaction (heat of reaction) approx. 3,600 kJ/kg HCl