A method for removing ammonia (NH3) from a gas produced in a pulp mill (100). The method comprises producing raw non-condensable gas comprising ammonia (NH3) in the pulp mill (100) and transferring at least some of the raw non-condensable gas to a scrubber (200) containing aqueous scrubbing solution (130, 140). The method comprises adding a compound capable of decreasing a pH of the scrubbing solution to the scmbbing solution (130, 140) and in the scrubber (200), contacting the raw non-condensable gas with the scmbbing solution (130, 140), to react the ammonia (NH3) of the raw non-condensable gas with the scmbbing solution to produce clean non-condensable gas and ammonium (NH4+). A pulp mill comprising equipment for performing the method.