Allied Group. Inc. introduced Coalescing Filters for natural gas applications on bus fleets. Compressed natural gas (CNG) is coalesced into an efficiency of 99.9999%, with pressures to over 4500psi. Allied's filter has a built-in prefilter and drain layer for extended life. Sizes range from as small as 0.18" I.D. to over 22" O.D. Microns range from 0.1 to over 100.