a multi - port system sampling maintains a balanced fluid flow , and more particularly is a gas sampling system used for the rapid detection of fire in which the flow rate through each sampling system aperture is substantially equal . the system may include a single main conduit having a number of sampling apertures spaced apart for sampling different locations . the sizing of the apertures is such that an equal flow rate is present at each aperture , allowing a balanced sampling of each sampling location . the system may also include multiple secondary conduits all feeding one main conduit . each secondary conduit has a number of different sampling apertures , and may be of a different length . the diameters of the secondary conduits are relative to the length of the conduits and the size of the respective conduit apertures so as to create a balanced fluid flow rate through each of the apertures .