whats the worlds most lethal chemical(gas)

Question: whats the worlds most lethal chemical(gas)
- Keywords:
  chemical,
  dangerous,
  deathly,
  gas,
  harmful
Asked by shadow3217 to Stuart, Alexander, Josh, Serena, Simone on 18 Jun 2013. This question was also asked by 309han472.
- Stuart Archer answered on 18 Jun 2013:
  
  One of the most lethal chemicals that has ever been made by humans is a nerve gas called VX – a horrible thing!
  
  In terms of things we use in the lab, hydrogen cyanide is probably the most commonly used lethal gas, although there are more exotic things like boron trifluoride that are also really nasty.

Question: whats the worlds most lethal chemical(gas)