The present invention relates to a three-phase separator (33) for separating off from a fluid gas and particles contained therein, comprising at least one pair of two gas collection caps (1, 2) extending in a horizontal longitudinal direction (L) and each having a plate section (3, 4). The plate sections converge in the downward direction. At the bottom ends the plate sections leave an inlet passage (7), elongated in the longitudinal direction, for the fluid containing particles and an outlet passage (8), elongated in the longitudinal direction, for settled particles. A discharge opening (9) for fluid, opening into the settling chamber, is provided at a level higher than the inlet and outlet passages. The inlet passage (7) and the outlet passage (8) are located in the extension of one another, viewed in the longitudinal direction. The surface area of the inlet passage is preferably greater than the surface area of the outlet passage. The discharge opening is provided level with or beyond the outlet passage.