An air handling unit for a data centre, a data centre comprising such, a method of operating such, and a method of cooling IT equipment in a data centre using such, is disclosed. The unit comprises an external airflow path (102) arranged to be in fluid communication with outside air, a separate internal airflow path (103) arranged to be in fluid communication with inside air, and heat tube panels (106). Preferably, each heat tube panel (106) comprises a heat tube comprising a first section in the external airflow path (102) and a second section in the internal airflow path (103). Preferably, the plurality of heat tube panels (106) is in a row across the internal and external air flow paths (103, 102). Preferably, at least one of the heat tube panels (106) is removable and extends through an opening between the internal and external air flow paths (103, 102).