Composite materials formed by impregnating a carbon or graphite fiber mat with plastic binders are being used increasingly in military, aerospace, sports and automotive applications. Carbon fibers are formed primarily from synthetic fibers carbonized in the absence of oxygen. Possibilities exist for the release of these fibers to ambient air during their formation, handling, weaving or impregnation, or during the manufacturing or incineration of composites. This study was concerned with characterizing the rate and physical/chemical properties of such emissions. Samples were collected from manufacturing operations. Operations considered included fiber winding, prepregging and weaving, as well as composity cutting, grinding, drilling, machining, sanding, and incineration. Release rates (fiber mass released per unit of material processed) ranged over several orders of magnitude with the largest releases being associated with weaving and incineration. Except for incineration where fiber diameters were reduced somewhat by burning, the original fiber diameters were maintained in the emitted material. Fiber lengths varied over wide ranges from tens to thousands of micrometers. Incineration experiments suggested that mechanical agitation and air flow in the incinerator would strongly affect releases. Electrical characterization of the fibers demonstrated that fibers will move and form chains in electrical fields.