We describe an experimental setup based on a sealed parallel-plate avalanche counter, which allows conversion electron Mössbauer spectroscopy at temperatures down to 120K. A study of the counting gas performances is carried out in order to find out the appropriate operating conditions. The detector can work in a wide range of pressures and voltages at room and low temperatures, for both iron- and tin-based Mössbauer transitions. An estimation of the gas gain is obtained by using a simple approach, which considers the avalanche gas process in parallel-plate geometry. The gas gain as a function of the filling pressure shows a maximum at room temperature and a monotonic increase at low temperature. The experimental setup has been tested with the determination of the Debye temperature of β-Sn, SnO2, and ε-FeSi.