The probability of defect catching microbes is proportional to the area of defect. Since pressure decay can detect only 100 micron defects while HIT detects 10 micron defects, the ratio of the areas is 100 times. Thus, risk of contamination of the bag is reduced by at least 100 times if HIT test is performed. This is conservative estimate that is based on defect area only. It does not take into account additional risk reduction associated with no observed penetration of aerosolized microbes through defects smaller than 10 micron.