Interlock for use in a process for degassing of a polymer powder in a degassing vessel. The interlock includes (a) measuring the temperature of the vapor phase resulting from a liquid-vapor separation, which vapor phase is used as a purge gas in a degassing vessel, (b) comparing the measured temperature to a threshold value, and (c) in the event that the measured temperature is above the threshold value then use of the vapor as purge gas is stopped or reduced.