Past accident surveys reveal that loading and unloading operations (LUOs) are responsible for 11% of fire-related domino accidents. This study investigates the domino accidents during LUOs in the last two decades and identifies the main causes and features of these domino effects. An index-based approach is proposed to assess these domino effects, measuring the periodic escalation capability of installations. The proposed escalation capability index takes into account the special features being present in these accidents, including the spread of vapor cloud due to delayed ignition, multiple fires caused by vapor cloud explosion (VCE), the quantity variation of hazardous substances, and the change of primary event risk due to operations. From a risk management view, an emergency strategy is proposed to tackle the risk caused by LUOs. Therefore, this methodology can identify the most critical areas with regard to the starting or escalating of domino events during LUOs and support the decision-making of alert levels.