Humidity sensing module for detecting humidity on at least one pre-determined humidity-prone zone Zj of at least one of the outer surfaces of the two outer layers of a printed circuit board, said printed circuit board being connected to a voltage source (Vcc), and comprising: - at least two electrically conductive layers (L 1... L n): • the first of the at least two electrically conductive layers being the ground plane (L 1) and • the other of at least two electrically conductive layer being a signal layer (L 2...L n) supporting electrical or electronical components wherein said humidity sensing module further comprises: - a transistor layer (L T) as a further signal layer, said transistor layer (L T) and said ground plane being connected to said voltage source (Vcc) by two resistors (R1, R2) configured to work as a voltage divider such us: • said ground plane is connected to voltage source (Vcc) by a first resistor and a second resistor, and • said transistor layer (L T) is connected to said voltage source (Vcc) between said first resistor and said second resistor, - a plurality of vias (Vi+, Vi-) arranged in pairs, such that: • the positive via of each pair (Vi+) has an end connected to at least one pre-determined humidity-prone zone Zj of one of the outer surfaces of the two outer layers and the other end connected to said transistor layer (L T); • the negative via of each pair (Vi-) has an end connected to at least one pre-determined humidity-prone zone Zj of the same outer surface of the two outer layers and the other end connected to said ground plane (L 1); - an external decision taking module (μC) connected between said two resistors (R1, R2), being configured to read the signal and interpret it depending on the different voltage level between said resistors (R1, R2), said humidity sensing module being configured such that when humidity between a positive via (Vi+) and a negative via (Vi-), placed at a predetermined distance (d) between them on the same outer surface, exceeds a humidity threshold, they become electrically connected determining a signal of different voltage level between said resistors (R1, R2) depending on the level of humidity and thus allowing said signal to be read and interpreted by said external decision taking module (μC). - at least two electrically conductive layers (L 1... L n): • the first of the at least two electrically conductive layers being the ground plane (L 1) and • the other of at least two electrically conductive layer being a signal layer (L 2...L n) supporting electrical or electronical components • the first of the at least two electrically conductive layers being the ground plane (L 1) and • the other of at least two electrically conductive layer being a signal layer (L 2...L n) supporting electrical or electronical components - a transistor layer (L T) as a further signal layer, said transistor layer (L T) and said ground plane being connected to said voltage source (Vcc) by two resistors (R1, R2) configured to work as a voltage divider such us: • said ground plane is connected to voltage source (Vcc) by a first resistor and a second resistor, and • said transistor layer (L T) is connected to said voltage source (Vcc) between said first resistor and said second resistor, - a plurality of vias (Vi+, Vi-) arranged in pairs, such that: • the positive via of each pair (Vi+) has an end connected to at least one pre-determined humidity-prone zone Zj of one of the outer surfaces of the two outer layers and the other end connected to said transistor layer (L T); • the negative via of each pair (Vi-) has an end connected to at least one pre-determined humidity-prone zone Zj of the same outer surface of the two outer layers and the other end connected to said ground plane (L 1); - an external decision taking module (μC) connected between said two resistors (R1, R2), being configured to read the signal and interpret it depending on the different voltage level between said resistors (R1, R2), - a plurality of vias (Vi+, Vi-) arranged in pairs, such that: • the positive via of each pair (Vi+) has an end connected to at least one pre-determined humidity-prone zone Zj of one of the outer surfaces of the two outer layers and the other end connected to said transistor layer (L T); • the negative via of each pair (Vi-) has an end connected to at least one pre-determined humidity-prone zone Zj of the same outer surface of the two outer layers and the other end connected to said ground plane (L 1); • the positive via of each pair (Vi+) has an end connected to at least one pre-determined humidity-prone zone Zj of one of the outer surfaces of the two outer layers and the other end connected to said transistor layer (L T); • the negative via of each pair (Vi-) has an end connected to at least one pre-determined humidity-prone zone Zj of the same outer surface of the two outer layers and the other end connected to said ground plane (L 1); - an external decision taking module (μC) connected between said two resistors (R1, R2), being configured to read the signal and interpret it depending on the different voltage level between said resistors (R1, R2),