To estimate process parameters for non-thermal methods of antimicrobial inactivation, the half-cycle method is very often used. However, the essential premise of this method of estimation, the independence of microbial inactivation kinetics from the microbial load, seems not to be true. Consequently, the attainment of the sterility assurance level as recommended by the pharmacopoeias by a process which has been validated using the half cycle method is not guaranteed. For the evaluation of such chemo-thermo disinfection processes, the quantification of remaining hepatitis B virus DNA (HBV-DNA) traces on the surface of instruments is a useful tool. An infection can be excluded if a decrese of the HBV-DNA residues on the instruments below the minimum infective dose can be demonstrated. Using the signal amplification technique to detect HBV-DNA on instruments, the safety of any reprocessing procedures can be improved.