By neglecting some elementary processes in the helium afterglow at intermediate pressures it is possible to simplify the system of differential equations which describe the time behaviour of discharge parameters, such as the electron temperature, the concentration of atomic and molecular ions and atomic and molecular metastable states.Simple expressions describing the time dependence of each of these parameters are obtained. Calculations based on these expressions agree in most cases with the experimental data available in the literature. The importance of processes which have been neglected is discussed.