This standard provides a separate calculation method for determining the contributing mass flow to be relieved resulting from each of the following specified conditions: - vacuum insulated vessels with insulation system (outer jacket + insulating material) intact under normal vacuum. Outer jacket at ambient temperature. Inner vessel at temperature of the contents at the relieving pressure; - vacuum insulated vessels with insulation system remaining in place but with loss of vacuum, or non vacuum insulated vessels with insulation system intact. Outer jacket at ambient temperature. Inner vessel at temperature of the contents at the relieving pressure; - vacuum or non vacuum insulated vessels with insulation system remaining fully or partially in place, but with loss of vacuum in the case of vacuum insulated vessels, and fire engulfment. Inner vessel at temperature of the contents at the relieving pressure; - vessels with insulation system totally lost and fire engulfment. Good engineering practice based on well established theoretical physical science shall be adopted to determine the contributing mass flow where an appropriate calculation method is not provided for an applicable condition.