#poison_gas  (chemical warfare) a gas that is poisonous to breath or contact
  supertype:  #gas  a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
  subtype:  #mustard_gas__mustardga__dichloroethyl_sulfide__dichloroethylsulfide__sulfur_mustard  a toxic war gas that raises blisters and attacks the eyes and lungs
  subtype:  #nerve_gas__nervega  a toxic war gas that is inhaled or absorbed through the skin and has harmful effects on the nervous and respiratory system

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