In this paper, we propose a new nonlinear f ltering algorithm that can provide more accurate and reliable localization compared with the pure particle f ltering (PF). In the proposed algorithm, failures of the PF are detected, and the failed PF is recovered using a f nite impulse response (FIR) f lter. The resulting f lter is called the combined particle/FIR f lter (CPFF). We demonstrate the performance of the CPFF by the indoor human localization.