Carbon tetrachloride, also known by many other names (the most notable being tetrachloromethane (also recognized by the IUPAC), carbon tet in the cleaning industry, Halon-104 in firefighting and Refrigerant-10 in HVACR), is an organic compound with the chemical formula CCl₄. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent. It is a colourless liquid with a "sweet" smell that can be detected at low levels.