its location and or ease of access such as the roof space of a house the receiving element is defined as any volumetric accommodating housing such as a cavity a gap or alternatively any surface onto which the fibers can come to rest according to the invention at least one roving 20 formed of at least one continuous bundle 21 of fibers is fed to a bundle spraying apparatus 30 such as the spray gun supplied with compressed air from a compressed gas source 40 such as a compressor or compressed gas reservoir and sprayed by the spraying apparatus in an expanded form into a receiving element to increase the fiber spray rate provision may be made for the spraying apparatus to be fed with several roving bundles 21 thus several rovings for example are paid out simultaneously the rovings being placed on their delivery palette at a distance from the point of spraying furthermore depending on the end use of the bulked product each roving may be made of a different material for example glass or thermoplastic for convenience and depending on the accessibility of the receiving element when just one feed roving 20 is enough this roving is then designed to be readily portable the roving is housed for example in a basket with a handle to make it easier to transport and to handle the roving during the fiber spraying operation it is also possible to find a roving support which is suitable for carrying on the operator 39 s back the spraying apparatus 30 is in the form of a.