"Carbon tetrachloride, also known by many other names (notably, carbon tet in the cleaning industry, and
as a Halon or Freon in HVAC, see Table for others) is the organic compound with the 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."