Tellurium hexafluoride
Tellurium hexafluoride is a colorless gas with a repulsive odor. It is very toxic by inhalation and skin absorption. When heated to high temperatures, it may emit toxic fluoride and tellurium fumes. It is heavier than air. Under prolonged exposure to fire or intense heat the containers may violently rupture and rocket. It reacts with water to yield toxic vapors.