Halon fire extinguishers were used extensively for fires on computers and electronic equipment. Portable extinguishers contained 'Halon 1211' and fixed systems used 'Halon 1301'. In the UK the use of Halon Fire Extinguishers are now prohibited except for use on aircraft and in the military and police. Halon 1211 (pronounced twelve-eleven) fire extinguishers contain a gas that stops the chemical reaction when fuels ignite and burn. HR3 fire extinguishers contain a proprietary blend of the "liquid streaming agent," Halon 1211, and the gaseous "total flooding agent," Halon 1301. The blend's power lies in the Halon 1301 is both a firefighting agent and a propellant.