An Operating theatre is provided with preconditioned air by a central Air Handling Unit ( AHU ). Nowadays, most hospital ventilation systems operate with a mixture of fresh and recirculation air. For operating theatres or minor surgery rooms to be upgraded or renovated, recirculation modules are an excellent alternative. Because many older facilities have insufficient space for bigger AHU’s and ducts etc, the recirculation module can be installed in either the ceiling ( Optivent ) or the wall ( Optiwall ). Here, the recirculation module will supply the recirculation air and the existing or new AHU will supply the fresh Air portion.