Abstract: Combination unit capable of use as a heat exchanger as well as for scrubbing particle-laden flue gases from a boiler, for instance. It comprises a casing inwardly divided into a lower chamber and an upper chamber, both chambers communicating by lateral baffled passages in which baffle members are disposed and water sprinklers are provided in such a manner as to create, in such lateral passages, a series of curtains of water through which the flue gases must pass in their way from the flue gas inlet, in the lower chamber, to the flue gas outlet, in the upper chamber. Simultaneously, banks of air conduits are provided in both chambers to recuperate heat from the hot flue gases. Water dripping from the aforesaid curtains is collected in the bottom of the casing and recirculated by the sprinklers after, occasionaly, having been filtered.