An air treatment system for a confined environment (C), 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 (C) 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 being arranged in fluid communication with the inlet port of said supply unit in correspondence of a circuit node (J), - a flow control valve arranged at said circuit node (J) 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 (C) 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 being arranged in fluid communication with the inlet port of said supply unit in correspondence of a circuit node (J), - a flow control valve arranged at said circuit node (J) 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 . <EOS>