An air treatment system for a confined environment, particularly a vehicle cabin, comprising: - a supply unit including an inlet port, a delivery port and a purge port, said supply unit being configured to deliver air to said confined environment through said delivery port, - a first filtering device having a first level of filtration, and a second filtering device having a second level of filtration, each of said first and second filtering devices (10, 12) being arranged in fluid communication with the inlet port of said supply unit in correspondence of a circuit node, - a flow control valve arranged at said circuit node and including a first working port in fluid communication with said first filtering device, a second working port in fluid communication with said second filtering device, a third working port in fluid communication with said inlet port, and a fourth working port in fluid communication with said purge port, the flow control valve further including: - a first operating position wherein a fluid communication is established between the first working port and the third working port, and a fluid communication is established between the second working port and the fourth working port, and - a second operating position wherein a fluid communication is established between the second working port and the third working port, and a fluid communication is established between the first working port and the fourth working port. - a supply unit including an inlet port, a delivery port and a purge port, said supply unit being configured to deliver air to said confined environment through said delivery port, - a first filtering device having a first level of filtration, and a second filtering device having a second level of filtration, each of said first and second filtering devices (10, 12) being arranged in fluid communication with the inlet port of said supply unit in correspondence of a circuit node, - a flow control valve arranged at said circuit node and including a first working port in fluid communication with said first filtering device, a second working port in fluid communication with said second filtering device, a third working port in fluid communication with said inlet port, and a fourth working port in fluid communication with said purge port, the flow control valve further including: - a first operating position wherein a fluid communication is established between the first working port and the third working port, and a fluid communication is established between the second working port and the fourth working port, and - a second operating position wherein a fluid communication is established between the second working port and the third working port, and a fluid communication is established between the first working port and the fourth working port. - a first operating position wherein a fluid communication is established between the first working port and the third working port, and a fluid communication is established between the second working port and the fourth working port, and - a second operating position wherein a fluid communication is established between the second working port and the third working port, and a fluid communication is established between the first working port and the fourth working port.