Meher-Homji et al.2 studied a wide range of 92 gas turbines to evaluate their sensitivity to an imposed level of fouling. Key results indicate that the net work ratio (Net work ratio = GT work output/ work from turbine) is a good predictor of both the gas turbine’s susceptibility to foul and its sensitivity to fouling. Low net work ratio engines where a higher portion of the total turbine work is consumed in the compressor tend to be both more susceptible and sensitive to axial compressor fouling.2 This is basically due to the fact that, for a given loss of compressor efficiency, the impact on power output is larger for a low NWR engine.