A three phase separator or settling device (2) or a digester (1) including the settling device. The settling device can receive a fluid containing liquid, gas and particulate material. The settling device includes a settling chamber to be filled with this fluid. The device can also include a liquid-discharge (5) for discharging liquid from the settling chamber and fitted close to the liquid level (30), a fluid inlet (6) for supplying the fluid into the settling chamber (3), a particulate material separation device (7) and a sludge outlet (8). A flow of fluid is provided into and out of the settling device and settling chamber. The inlet includes a gas separation device (4) for separating gas from the fluid including channels, the inlet positioned close to the fluid level. The inlet and transition (75) into the settling chamber is arranged to create a pre-separated flow pattern including a generally laminar liquid flow.