New Greenhouse Gas Identified, Potent and Rare (but Expanding). Trifluoromethyl sulfur pentafluoride (SF5 CF3) so far occurs in the atmosphere in a concentration of one part in ten trillion, but its concentration appears to be steadily rising and it traps heat more effectively than all other known greenhouse gases. What’s more, once produced, it probably takes over 1,000 years to break down. Its source is a mystery. Speculation hinges upon a secret military or industrial use or an inadvertent byproduct of some industrial process. The similar gas SF6 is used in electronics and weaponry production. New York Times