Filter process validation is performed ideally with the product to be filtered under the process conditions of the filtration activity at the end-user. If there is an elevated temperature the bacteria challenge test requires to be performed under this elevated temperature, as long as the organisms are viable at that temperature. A viability test under these conditions is necessary to determine whether the organisms are viable or not. If the temperature is too high and the organism shows mortality, one has evidence that the organism does not survive. At that point one reduces the temperature to reach viability and runs the product bacteria challenge test at these modified conditions.