Abstract: A heat and moisture exchanger, comprises a rigid monolithic body (101). The rigid monolithic body (101) comprises a circumferential wall (102); and a structure of interconnected elements (106) surrounded by the circumferential wall (102). The structure (106) is open to fluid communication through the structure (106) between a first side (114) of the structure and a second side (115) of the structure (106) opposite the first side (114) of the structure (106). The circumferential wall (102) extends from the first side (114) to the second side (115) of the structure (106). The heat and moisture exchanger (100) is open on both of the first side (114) and the second side (115) of the structure (106), to allow fluid communication between the structure (106) and an exterior of the heat and moisture exchanger (100) on both sides (114, 115).