Perfluorocarbon-based blood substitutes are completely man-made; this provides advantages over blood substitutes that rely on modified hemoglobin, such as unlimited manufacturing capabilities, ability to be heat-sterilized, and PFCs' efficient oxygen delivery and carbon dioxide removal. PFCs in solution act as an intravascular oxygen carrier to temporarily augment oxygen delivery to tissues. PFCs are removed from the bloodstream within 48 hours by the body's normal clearance procedure for particles in the blood – exhalation. PFC particles in solution can carry several times more oxygen per cubic centimeter (cc) than blood, while being 40 to 50 times smaller than hemoglobin.