Butane (n-butane) and propane are used as aerosol propellants both in the United States and Europe. The purity of the butane-propane mixture used in the aerosol industry is different from that used as fuel gas, and the butane content of the former is usually a mixture of butane and isobutane in an approximate ratio of 3:1. Butane is also used as a fuel and as a starting material for polymerization plants to convert it to iso-octane which in turn is used to increase the antiknock rating of aviation and motor fuel. The inhalation of butane in the anesthetized open-chest dog preparation brought about the following hemodynamic effects: a, decrease in cardiac output, left ventricular pressure, stroke volume, and stroke work in as low a concentration as 0.5%. b, decrease in myocardial contractility, and c, decrease in mean aortic pressure.