Halons are known to be the most effective fire extinguishers in the aviation industry. They are gaseous when discharged, non-conductors of electricity and extinguish fires by disrupting the chemical reaction causing them.
There are two variants of Halon:
Halon 1211 - This is a steaming agent and is used solely in portable extinguishers.
Halon 1311 - This is a flooding agent and is typically used in fixed-location extinguishers such as cargo holds and engines.
Despite the efficacy of Halon fire extinguishers, they have been detected to cause damage to the ozone layer and thereby, not suitable for regular and non-essential use. The search for alternatives to Halon extinguishers has been underway for over two decades now.