Abstract: The present invention comprises a helmet (1) intended to surround the skull of a user (10); wherein the helmet (1) comprises a storage chamber (14) in a rear portion of the helmet (1), and which contains a pressurized gas; an activation mechanism to expand the expandable gas; at least one sensor (5), to detect an imminent accident; a bag (13) housed in the back of the helmet (1), connected to the compressed gas; and a control device (3), for inflating the bag (13) with the expanded pressurized gas moments before an accident detected by the sensor or sensors (5); wherein the bag (13), once inflated (2), emerges from the rear portion of the helmet (1), intended to protect the lateral area of the neck, the cervical area and the base of the skull.