An HME has a housing (10) moulded in two parts (26 and 27) of a thick, thermally-insulative foamed plastics to form an enlarged central region (13) and opposite end walls (24 and 25). Separate patient and machine end couplings (11 and 12) are bonded to openings (37 and 47) in the end walls. The two housing parts (26 and 27) are bonded end to end about an HME element (14) formed by a strip of treated corrugated paper wound about a support sleeve (50).
