The venturi mask, also known as an air-entrainment mask, is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy.[1][2] The mask was invented by Moran Campbell at McMaster University Medical School as a replacement for intermittent oxygen treatment. Dr. Campbell was fond of quoting John Scott Haldane's description of intermittent oxygen treatment; "bringing a drowning man to the surface – occasionally".[3][4] By contrast the venturi mask offered a constant supply of oxygen at a much more precise range of concentrations.