Hydrogen elimination mechanisms involved in the low-pressure chemical vapor deposition of silica films from SiH4/O-2/N-2 mixtures are investigated. The main purpose of this work is to elucidate the mechanisms that limit hydrogen elimination in the silica deposition process under the mass-transport and gas-phase kinetic regimes. To this end, different gas-phase, surface, and mass-diffusion processes relevant to the SiH4 oxidation and silica growth chemistry are considered and discussed on the basis of the influence of temperature, total gas flow rate and O-2-to-SiH4 flow ratio on deposition rate and hydrogen content in the film, as determined by infrared spectroscopy and elastic recoil detection analysis. Our results indicate a clear relationship between the growth and hydrogen elimination kinetics, and support a hydrogen elimination model based on radical surface interactions.