Platinum catalysts are used to convert methyl alcohol vapors (CH4O) into formaldehyde (CH2O) on contact, glowing red hot in the process. This effect is used to make small hand warmers. Platinum is also used in a device called a catalytic converter, a device found in the exhaust systems of most cars. Catalytic converters combine carbon monoxide (CO) and unburned fuel from a car's exhaust with oxygen from the air, forming carbon dioxide (CO2) and water vapor (H2O). Platinum is also used as a catalyst in the production of sulfuric acid (H2SO4) and in the cracking of petroleum products. Fuel cells, devices that combine hydrogen and oxygen to produce electricity and water, also use platinum as a catalyst.