  Photon number resolving monitoring is a practical light source monitoring
scheme in QKD systems, which reduces the impacts from untrusted sources
effectively. This scheme requires a single photon detector, normally working at
low temperature to suppress its dark count rate. In this paper, we use a
room-temperature detector and show that the dark count rate is irrelevant to
the monitoring performance in our scheme, which can sufficiently relax
requirements on the detector's working conditions as well as integration
complexity, and this would be highly demanded for practical systems.
Furthermore, influences of parameter drifts at room temperature are analyzed,
and the monitoring scheme is testified in a real QKD system.
