Air treatment apparatus

An air treatment apparatus for an operator environment of an agricultural vehicle in which air to be filtered is drawn into an air filtration system, filtered and directed to an HVAC system, in which the HVAC system comprises an inlet plenum, at least one blower, other HVAC components and an outlet to the operator environment;

• wherein the air filtration system comprises:
• at least one external inlet;
• a first filtration device comprising a first coarser level of filtration located between the at least one external inlet and the HVAC inlet plenum;
• a second filtration device comprising a second finer level of filtration located between the at least one external inlet and the HVAC inlet plenum;
• a first air filtration system blower connected to the HVAC inlet plenum;
• a valve mechanism which selectively connects either the first filtration device to the HVAC inlet plenum or the second filtration device to the HVAC inlet plenum;
• and for each filtration device, a respective bypass is permanently connected with an inlet end downstream of the valve mechanism and an outlet end upstream of the valve mechanism and adjacent the respective filtration device such that in use a portion of air flow downstream of the valve mechanism may be recirculated to purge the respective filtration device, and each bypass includes a respective non-return valve opposing transit of air from the outlet end to the inlet end.