A liquid separator is provided with a vessel which defines a space which is sealed at the top by a lid in which is situated an outlet. A pipe is provided in the space extending round the outlet in the space, as of the lid. A fine filter also extends in the space round the outlet such that between the pipe and the fine filter is defined an outlet zone which is connected to the environment by means of a safety valve. The safety valve is connected to the outlet zone via a passage in the lid.