Overpressure is one important cause of domino effect in accidents of chemical process equipments. Damage probability and relative threshold Value are two necessary parameters in QRA of this phenomenon. Some simple models had been proposed based on scarce data or oversimplified assumption. Hence. more data about damage to chemical process equipments were gathered and analyzed. a quantitative relationship between damage probability and damage degrees of equipment was built. and reliable probit models were developed associated to specific category of chemical process equipments. Finally, the improvements of present models were evidenced through comparison with other models in literatures, taking into account Such parameters: consistency between models and data, depth of quantitativeness in QRA. (c) 2008 Elsevier B.V. All rights reserved.