A safety device for a tank intended to contain a pressurized gas, comprising: - an ventilation channel intended to establish fluid communication between an internal volume delimited by the tank and the outside of the tank, - a safety piston movable between a closure position in which it closes the ventilation channel, and a safety position in which it does not close the ventilation channel, - a first safety member which is deformable and configured to hold the safety piston in the closure position against an elastic return force returning the safety piston in the safety position, the safety device further comprising: - deformation means for deforming the first safety member, wherein the deformation means are movable between a resting position and a deformation the first safety member position, and - at least a second safety member intended, in a resting position, to hold the deformation means in the resting position against an elastic force returning the deformation means in the deformation of the first safety member position when the second safety member is subjected to a temperature below a predetermined temperature and, in a working position, to release the elastic force returning the deformation means in the deformation of the first safety member position when the second safety member is subjected to a temperature higher than the predetermined temperature, wherein the second safety member is formed by a safety cable made of a material having low mechanical fire resistance. - an ventilation channel intended to establish fluid communication between an internal volume delimited by the tank and the outside of the tank, - a safety piston movable between a closure position in which it closes the ventilation channel, and a safety position in which it does not close the ventilation channel, - a first safety member which is deformable and configured to hold the safety piston in the closure position against an elastic return force returning the safety piston in the safety position, the safety device further comprising: - deformation means for deforming the first safety member, wherein the deformation means are movable between a resting position and a deformation the first safety member position, and - at least a second safety member intended, in a resting position, to hold the deformation means in the resting position against an elastic force returning the deformation means in the deformation of the first safety member position when the second safety member is subjected to a temperature below a predetermined temperature and, in a working position, to release the elastic force returning the deformation means in the deformation of the first safety member position when the second safety member is subjected to a temperature higher than the predetermined temperature, - deformation means for deforming the first safety member, wherein the deformation means are movable between a resting position and a deformation the first safety member position, and - at least a second safety member intended, in a resting position, to hold the deformation means in the resting position against an elastic force returning the deformation means in the deformation of the first safety member position when the second safety member is subjected to a temperature below a predetermined temperature and, in a working position, to release the elastic force returning the deformation means in the deformation of the first safety member position when the second safety member is subjected to a temperature higher than the predetermined temperature, wherein the second safety member is formed by a safety cable made of a material having low mechanical fire resistance.