The so-called blow-through theory, when organisms supposedly are pushed through a membrane by elevated pressure has yet to be proven. It has been determined that organisms like mycoplasma can be pushed through a membrane at elevated pressures, but typically one would not find mycoplasma as a contaminant during terminal filtration. However, if there is the risk of a native organism being pushed through the membrane matrix product bacteria challenge tests need to be performed to determine whether this happens or not. Similar to the potential damage of the filter by a drying cycle at elevated differential pressure, the risk requires to be tested.