Abstract: Disclosed is a new fluid ionizer for use within a dielectric conduit through which a fluid containing particulate impurities is flowing. The ionizer causes the impurities to cluster together to form larger particles which may be more easily filtered by subsequent processes. The fluid ionizer comprises a hollow electrically grounded first electrode disposed within the conduit and through which fluid flowing in the conduit also flows. A second electrode, coaxially positioned within the first electrode, has a plurality of pointed prongs projecting laterally therefrom to define an ionizing comb. The fluid flows amongst the prongs of the ionizing comb. The second electrode is negatively charged with a high frequency series of high voltage pulses whereby the second electrode, and more particularly the points of the ionizing comb, imparts a negative charge to some of the particles. The negatively charged particles attract the remaining naturally positively charged particles to form clusters of particles.