This report presents a study of the effect of reusing experience in the Hazards and Operability Analysis method (HazOp method) with regards to how the effectiveness of the method is affected. The study was conducted by first creating a software tool for experience reuse in HazOp, then testing that tool in a student experiment in which the participants used the tool when conducting a HazOp. During the experiment it was found that students using the tool found 21% more hazards in the system under study than their counterparts. After conducting the experiment it was found that there was a 94% certainty that this improvement was not due to random effects.