One resistive plate chamber made of Chinese materials and one Italian resistive plate chamber have been tested in the Gamma Irradiation Facility (GIF) at CERN on a high intensity muon beam together with a 137Cs source to give a uniform photon background, and simulating conditions close to those expected for an LHC muon detector. The results are analyzed. Good space and time resolutions are obtained which satisfy the future CMS experiment requirements. The detection efficiency is different between two RPCs against a high irradiation background. The reason is discussed.