A switch includes an insulative housing, a pair of first and second contacts fixed in the insulative housing and a dome-shaped moveable contact. The insulative housing includes a receiving space and a first peripheral wall located outside of the receiving space. The first and the second contacts include first and second contacting sections, respectively. The first and the second contacting sections are separated a distance from each other and exposed in the receiving space. The dome-shaped moveable contact is mounted in the receiving space under condition that the moveable contact is constantly in contact with the second contacting section while the moveable contact is alternatively driven to engage with the first contacting section so as to establish electrical connection between the first contact and the second contact. The first peripheral wall defines a sinuated air-passageway communicating the receiving space to outside.