Sterilization filter allows for the exclusion of organisms based upon size. There are many types of filtration techniques, but when sterilizing a system membrane filtration is used. Membrane filtration traps contaminants larger than the pore size on the surface of the membrane. 

If contaminants are smaller than the desired particle, decrease the membrane pore size and trap the product while passing the contaminants through the membrane. For greater system flexibility, sterilization filters can be added in parallel or series. 

When adding a sterilization filter of same pore size, in parallel, throughput increases. If instead a sterilization filter of differing pore size was added in series, separation of multiple microorganisms are possible.