Collecting chamber and fiber formation method solve technical problems of formation of vortices and recirculations within collecting chamber of melt fiberization apparatus, bonding of fiber to walls of collecting chamber, presence of shot in primary layer of fiber deposited onto perimeter wall of collecting drum of collecting chamber, and non-uniform deposition of fiber into primary layer of fiber deposited onto perimeter wall of collecting drum of collecting chamber by slanting at least one wall or ceiling of a collecting chamber in order to reduce onset of vortices-and recirculation especially at high mass flow of fiber and high gradients of multi phase flow velocity. Further, by adding shot collectors amount of shot reducing heat transfer properties of fiber is reduced. In addition, adding slats for additional air inlet to further reduce vortices-and recirculation as well as adding balancing air flow induced by fan within drum assembly comprised of perforated surface is contributing to solution of technical problem at hand. Basic goals of proposed solution are: achieve high mass flow of fiber with low vortices and recirculation, and with minimum tear of primary layer of fibers collected on surface of collecting chamber drum assembly, and - separation of shot from fiber at the onset of fiber transport from a spinner.