A HVAC pre-filter system for a vehicle, the system comprising: a HVAC outlet for connection with a HVAC inlet arranged to provide airflow to a vehicle HVAC system ; a cab inlet for connection with a cab outlet arranged to provide airflow exiting from a vehicle cab ; and at least a first inlet/outlet arranged to be connected to ambient air, a pre-filter provided in said first inlet/outlet, characterised in that the pre-filter system further comprises at least a second inlet/outlet arranged to be connected to ambient air, a pre-filter provided in said second inlet/outlet, and a flow direction system arranged to switch between: (i) a first state, where said at least a first inlet/outlet is connected to said HVAC inlet to provide ambient air to a vehicle HVAC system and where said second inlet/outlet is connected to said cab outlet such that airflow exiting from a vehicle cab to the ambient air acts to clean the pre-filter of said second inlet/outlet, and (ii) a second state, where said at least a first inlet/outlet is connected to said cab outlet such that airflow exiting from a vehicle cab to the ambient air acts to clean the pre-filter of said at least a first inlet/outlet and where said second inlet/outlet is connected to said HVAC inlet to provide ambient air to a vehicle HVAC system. a HVAC outlet for connection with a HVAC inlet arranged to provide airflow to a vehicle HVAC system ; a cab inlet for connection with a cab outlet arranged to provide airflow exiting from a vehicle cab ; and at least a first inlet/outlet arranged to be connected to ambient air, a pre-filter provided in said first inlet/outlet, characterised in that the pre-filter system further comprises at least a second inlet/outlet arranged to be connected to ambient air, a pre-filter provided in said second inlet/outlet, and a flow direction system arranged to switch between: (i) a first state, where said at least a first inlet/outlet is connected to said HVAC inlet to provide ambient air to a vehicle HVAC system and where said second inlet/outlet is connected to said cab outlet such that airflow exiting from a vehicle cab to the ambient air acts to clean the pre-filter of said second inlet/outlet, and (ii) a second state, where said at least a first inlet/outlet is connected to said cab outlet such that airflow exiting from a vehicle cab to the ambient air acts to clean the pre-filter of said at least a first inlet/outlet and where said second inlet/outlet is connected to said HVAC inlet to provide ambient air to a vehicle HVAC system. (i) a first state, where said at least a first inlet/outlet is connected to said HVAC inlet to provide ambient air to a vehicle HVAC system and where said second inlet/outlet is connected to said cab outlet such that airflow exiting from a vehicle cab to the ambient air acts to clean the pre-filter of said second inlet/outlet, and (ii) a second state, where said at least a first inlet/outlet is connected to said cab outlet such that airflow exiting from a vehicle cab to the ambient air acts to clean the pre-filter of said at least a first inlet/outlet and where said second inlet/outlet is connected to said HVAC inlet to provide ambient air to a vehicle HVAC system. <EOS>