There are several sources for possible errors when numerical gas explosion simulators are applied to estimate loads on structures and equipment, The present paper proposes a partial coefficient method to deal with uncertainties that arises from variations of the location of the ignition source, and the lack of knowledge of size and location of the exploding gas cloud. The method also describes how to take into account physical and numerical idealization errors of the current available explosion simulators, The paper describes the procedure to calculate distribution quantiles for explosion parameters such as pressure and impulse with appropriate confidence levels, Non-parametric statistics are used to generalize and quantify the effect of the ignition point location in several offshore modules. The coefficients to achieve reasonable levels of safety are provided for these cases, Existing explosion simulator validation data are used to provide acceptable levels of safety in the estimation of gas explosion parameters, (C) 1997 Elsevier Science Ltd, All rights reserved.