Halons are powerful ozone-depleting chemicals, which contain bromine. They have been used in fire protection applications to suppress or extinguish fires, especially in occupied spaces and critical operations. They are controlled under the Montreal Protocol.
Many land-based and commercial maritime applications that previously used halons for fire protection have switched to alternatives. However, halons are still used in aviation, military applications, nuclear power stations and the petrochemical industry. After military applications, aviation is the largest use of halons and is increasing.
But the diminishing and uncertain supply of halons, combined with the uncertainty surrounding the identification and installation of suitable alternatives, presents significant current and future risks to the aviation sector. Particularly in view of their continued need. Careful management of halon reserves is critical for the aviation sector to maintain supply of halon to meet global fire protection needs until the lengthy process of identifying and implementing safe and effective alternatives is successful.
There are different types of halons. Halon 1211 is used in aviation for cabin handheld portable fire extinguishers. Halon 1301 is used for in-built lavatory trash receptacles extinguishers (lavex), engine nacelles/auxiliary power units and cargo compartments on aircraft. Halons that are recovered from applications such as shipping and computer rooms are recycled to supply on-going halon uses, including aviation.
The Montreal Protocol phased out the production, import and export of halons in non-Article 5 parties (developed countries) in 1994 and in Article 5 parties (developing countries) in 2010. These control measures apply to newly manufactured halon, not to recycled halons. Recycling remains the sole source of halons for fire protection applications where alternatives are still under development or legacy systems are in transition, as in aviation.
Under the Montreal Protocol, essential use exemptions for bans on production and consumption of halons are only available in exceptional circumstances and are decided on eligibility against strict criteria. Recovered and recycled halons have been available in sufficient quantity and quality for continued use in aviation. For this reason, halons 1211 and 1301 have not qualified for these production and consumption exemptions.
The search for alternatives to halons in aviation began more than 25 years ago. There are many challenges in identifying, certifying, commercialising and implementing fire protection agents for aviation applications because of the required high levels of safety. Alternatives must meet stringent fire standards, safety and toxicity requirements, satisfy weight and size restrictions, and pass prescribed certification tests. The process and timelines are lengthy for development and certification of successful alternatives: the duration from new design aircraft certification to aircraft production is about 10 years. These factors narrow the pool of prospective fire protection agents and lengthen the duration of the search for and introduction of successful candidates.
Following extensive research and development, replacements are available for halon 1211 for cabin handheld extinguishers and for halon 1301 for in-built lavatory trash receptacle extinguishers on aircraft. Non-halon fire protection agents for these two applications are now being fitted in new aircraft and in existing older aircraft where retrofit is feasible. Alternatives to halons in aviation include high global warming potential hydrofluorocarbon chemicals (HFCs): HFC-227ea and HFC-236fa. For the lavex application, these two HFCs are the only alternatives to halon 1301 currently available. However, the Kigali Amendment to the Montreal Protocol requires that the production and consumption of HFCs be phased down over specified periods.
Acceptable alternatives to halon 1301 are not available for larger fire protection systems on aircraft, i.e., engine nacelles/auxiliary power units and cargo compartments. Alternative fire suppression systems for aircraft engine nacelle and auxiliary power units or cargo compartments face many hurdles in their development. In recent years, transnational consortia of aircraft manufacturers and stakeholders have been established to accelerate the development of alternatives for these applications. Potential alternative agents are in early stages of qualification. However, there is no guarantee of success.
The Montreal Protocol, through its Halons Technical Options Committee, has been working with the International Civil Aviation Organisation (ICAO) to support the on-going management of halons and their replacement with alternatives for aviation fire protection. ICAO has developed mandated requirements for the staged replacement of halons in aircraft when alternatives are predicted to be available. These requirements signal target dates for different aircraft applications for the replacement of halons in current production or new design aircraft. Member States can submit “differences” that declare an intention not to meet these target dates. Some have filed differences for engine nacelle/auxiliary power units and cargo compartments. With no currently available non-halon agents for cargo compartments and engine/auxiliary power units, halon 1301 is still likely to be installed in new production aircraft for the next 20-40 years1.
Other than a very small number of countries that hold stockpiles of halons to supply their uses, most recycled halons are made available through just-in-time commercial international and intranational trade in recovered halon. There are challenges associated with the available global reserves of recycled halons in supplying remaining fire protection applications. Reserves are finite and diminishing with continued halon usage. The global supply, distribution and demand for recycled halon is unbalanced.
There are regional barriers to the availability of recovered halons to supply aviation uses. For example, halon recovery and recycling companies have experienced difficulties in shipping recovered bulk halons across international borders due to their misclassification by some authorities as “hazardous wastes”, triggering restrictions under the Basel Convention. The Basel Convention is the international treaty to protect human health and the environment from the adverse impacts of hazardous wastes and restricts their transboundary movement.
Increasingly, contaminated recovered halon is presenting a challenge for recycling, with additional effort, cost and losses associated with reclamation and purification of contaminated halon for safe reuse in aviation. Aviation procedures specify that recycled halons must be certified to meet international standards (ISO 7201 for halon 1211 and ASTM D 5632 Type 2 for halon 1301). Best practice management by airlines and their contractors is needed to avoid halon contamination during servicing of fire protection equipment.
But the diminishing and uncertain supply of halons, combined with the uncertainty surrounding the identification and installation of suitable alternatives, presents significant current and future risks to the aviation sector. Particularly in view of their continued need. Careful management of halon reserves is critical for the aviation sector to maintain supply of halon to meet global fire protection needs until the lengthy process of identifying and implementing safe and effective alternatives is successful.
1UNEP, Report of the Technology and Economic Assessment Panel, Volume 2, Decision XXIX/8 Report on the future availability of halons and their alternatives, September 2018.
