Abstract: Pressure relieving fluid containers which provide a controlled rupture and pressurized fluid release when the pressure exerted on the container reaches a predetermined level. A substantially frustum-shaped indentation is included in a wall of the container and at least one score is formed on the part of the wall containing the indentation defining a rupture detachable blowout area. The frustum-shaped indentation is of a size with respect to the thickness of the wall containing it whereby when a predetermined fluid pressure is exerted on the wall, the indentation inverts and tears along the line of weakness created by the score thereby opening the portion of the wall corresponding to the blowout area and relieving fluid pressure therethrough.