A novel multiple stage separator (MSS) vessel is disclosed wherein the vessel includes at least first and second stages or decks of separation cyclones, the stages arranged for operation in series. Each stage or deck includes an upper and lower tube sheet on which a plurality of cyclones are installed, solid particles in the gas stream being separated from the stream and dispensed between the tube sheets as the stream passes through each stage. The vessel has an inlet to receive a gas stream containing the particulates, and the flow travels typically downwardly, first passing through the first stage, then passing through at least a second stage. When implemented downstream of a fluid catalytic cracking (FCC) unit, the MSS has been found to remove a surprisingly increased amount of particulates over a conventional third stage separator (TSS), which contains a single stage separator.