Abstract: Wet scrubbing process for cleaning waste gases containing formaldehyde such as those produced in the manufacture of fiber glass insulation has substantial advantages over alternative thermal incineration process in that it requires less capital equipment expense and utilizes far less energy for handling equal volumes of waste gases. The gases are scrubbed in two scrubbing zones, the first of which contains hexamethylenetetramine and ammonium hydroxide to which ammonia is added and the second of which has water added to it. A part of the second scrubbing solution is introduced into the first scrubbing solution and a part of the first scrubbing solution is drawn off from the system.