Ventilation is a process of gas exchange between the lungs and the environment whereas ventilator is a device that assists in the ventilation process when the person is unable to do so by himself. Iron lung (also known by names of Tank ventilator or Drinker tank) is a type of mechanical ventilator discovered by Philip Drinker.This ventilator is a negative pressure ventilator (NPV) which works by applying negative pressure to the abdomen or body in order for the lungs to expand (forced inhalation). The pressure was then released resulting in natural exhalation due to elastic recoil of alveoli. Iron lung consists of a horizontal chamber where the person was laid with his head outside the chamber. The pressure inside the chamber was changed with the help of vacuum pumps. This ventilator was a major standby treatment in the ICU for children suffering from polio but now it's use is obsolete.