Mephitic

a.
  1. Tending to destroy life; poisonous; noxious; as, mephitic exhalations; mephitic regions.
  2. Offensive to the smell; as, mephitic odors.
    3. Mephitic air (Chem.),
    carbon dioxide; -- so called because of its deadly suffocating power. See Carbonic acid, under Carbonic.