Under the Kigali Amendment, reductions in hydrofluorocarbon‑23 (HFC‑23) will begin in 2024 and proceed on a phased-out basis. However, the impact on HFC‑23 in the short term will be limited and will not affect design or application.

Shi Zhengrong: An analysis of the impact of the Kigali Amendment to the Montreal Protocol on heptafluoropropane fire‑extinguishing agents, along with a review of current applications and alternative technologies, providing valuable guidance for industry development.

(1) In accordance with the Kigali Amendment, reductions in hydrofluorocarbon‑23 (HFC‑23) will begin in 2024, with a phase-out scheduled to take place gradually. However, the impact on HFC‑23 in the short term will be limited and will not affect design or application.

(2) In practical applications, we should proactively respond to policy requirements and promote the adoption of alternatives to heptafluoropropane.

(3) Ultra-fine dry powder cannot be regarded as a substitute for heptafluoropropane and shall not be used in areas requiring gaseous fire suppression systems.

(4) The main alternatives to heptafluoropropane include inert gases, perfluorohexanone, and fine-water-mist fire suppression systems.

Decomposed as follows:

Key Point 1: Heptafluoropropane, halons (1211 and 1301), and the Montreal Protocol and the Kigali Amendment.

(1) The Montreal Protocol and halon fire-extinguishing agents (1211, 1301).

The Vienna Convention for the Protection of the Ozone Layer, concluded in 1985, serves as a crucial legal foundation for global efforts to protect the ozone layer. The Montreal Protocol on Substances that Deplete the Ozone Layer, commonly referred to as the Montreal Protocol, was adopted in 1987 with the aim of phasing out the production and use of ozone-depleting chemicals. China became a Party to the Protocol in 1991, imposed restrictions on the use of halons starting in 1994, completely phased out 1211 by 2005, and ceased production of 1301 by 2010.

As a transitional substitute for halon fire suppressants (1211 and 1301), heptafluoropropane boasts advantages such as cleanliness, high efficiency, and low storage pressure. Over the past two decades, it has been widely adopted and has become the gas‑based fire suppressant with the largest market share.

 

(2) The Kigali Amendment and heptafluoropropane, hexafluoropropane, and trifluoromethane.

In 2016, the Parties to the Montreal Protocol adopted the Kigali Amendment, which aims to limit and control the greenhouse gas hydrofluorocarbons (HFCs). HFCs are a class of potent synthetic greenhouse gases used in sectors such as automotive air conditioning, residential refrigeration, commercial and industrial refrigeration, fire suppression, foam production, and aerosol propellants. The Kigali Amendment regulates 18 HFCs, including the gaseous fire‑extinguishing agents heptafluoropropane (HFC‑227ea), hexafluoropropane (HFC‑236fa), and trifluoromethane (HFC‑23). Hexafluoropropane and trifluoromethane are now rarely employed as fire‑extinguishing agents and are therefore not discussed further in this paper.

The amendment establishes a phase-down schedule for HFCs: the first group of developing countries, including China, shall freeze the production and consumption of controlled‑use HFCs at baseline levels starting in 2024; from 2029, production and consumption shall not exceed 90% of the baseline; from 2035, not more than 70%; from 2040, not more than 50%; and from 2045, not more than 20%. Accordingly, beginning in 2024, heptafluoropropane fire‑extinguishing agents will be subject to production quotas.

Note: Heptafluoropropane is also known as FM‑200. FM‑200 was originally developed by DuPont in the United States and marketed under the trade name FM‑200; the trademark is currently owned by Chemours, a chemical company spun off from DuPont.

 

Key Point 2: The impact of the Montreal Protocol and the Kigali Amendment on gaseous fire suppression systems.

The Montreal Protocol has already phased out halon fire suppressants (1211 and 1301), while the Kigali Amendment, effective from 2024, will reduce and eventually phase out hydrofluorocarbon‑23.

Starting in 2024, China will annually publish the “Annual Production Quota for Hydrofluorocarbons (HFCs).” All enterprises producing HFCs must ensure that their production capacity does not exceed the allocated quota, and this includes heptafluoropropane fire‑extinguishing agents. In other words, the maximum annual output of all manufacturers of heptafluoropropane fire‑extinguishing agents is capped and will be progressively reduced, with production slated to cease by 2045.

Among current gaseous fire‑extinguishing systems, heptafluoropropane accounts for the largest share. The Kigali Amendment’s reduction in heptafluoropropane production will inevitably affect the selection and application of such systems, accelerating their upgrade and replacement.

It should be noted that halon‑free fire suppression systems already in service are not subject to the Kigali Amendment and may be maintained and serviced in accordance with applicable regulations without affecting their normal operation.

 

Key Point 3: In the short term, the Kigali Amendment will have limited impact on heptafluoropropane, and it can still be designed for use.

According to the HFC phase-down schedule under the Kigali Amendment, by 2029, HFC reductions will amount to only 10%. It can be assumed that, over the next three to five years, applications of heptafluoropropane will not be significantly affected.

In principle, heptafluoropropane can still be designed and used as usual; however, its phase-out is an inevitable trend. In practical applications, it is essential to proactively comply with policy requirements and promote the adoption of alternative fire‑extinguishing agents.

 

Key Point 4: Alternatives to heptafluoropropane: inert gases, perfluorohexanone, and fine-water-mist fire suppression systems.

The main alternative systems to heptafluoropropane include inert gas systems (such as IG541 and IG100), perfluorohexanone, and fine water mist systems, which are described below:

(1) Inert gas fire suppression systems (e.g., IG541, IG100).

Inert gas fire suppressants are formulated by blending one or more of the following gases—nitrogen, argon, and carbon dioxide—at specified proportions (excluding carbon dioxide). Inert gas fire suppressants are also known as the IG series; the “IG” derives from INERGEN. The numerical code following “IG” indicates the respective volumetric fractions of nitrogen, argon, and carbon dioxide.

Note: INERGEN is a fire-suppression agent trademark developed and registered by the U.S. company ANSUL, and it is currently owned by Johnson Controls.

1. Fire-extinguishing mechanism

Asphyxiation fire suppression.

2. Safety Performance

In most applications, the extinguishing concentration of inert-gas fire suppressants does not exceed the threshold for toxic effects, ensuring a high level of safety and making them suitable for occupied spaces.

3. Main Categories

Based on the type of extinguishing agent, inert gas fire suppressants mainly include IG541, IG01, IG100, and IG55; among these, IG541 and IG100 are the most widely used. The composition of IG541 is identical to that of INERGEN (a halon‑free extinguishing agent).

4. Application Prospects.

Inert gas fire suppressants are all atmospheric constituents, sourced from natural or industrial by-products, making them purely “green” gaseous extinguishing agents and the most ideal alternative to heptafluoropropane.

At present, inert-gas fire-extinguishing systems rated at 15 MPa and 20 MPa have reached a mature stage and hold promising prospects for widespread application.

 

(II) Perfluorohexanone fire suppression system.

Perfluorohexanone fire suppressant (FK‑5‑1‑12), also known as Novec 1230. Novec 1230 is a trademarked name developed and registered by the U.S.-based company 3M.

Perfluorohexanone is a liquid at ambient temperature and pressure, with a low boiling point of 49°C. Upon release into the fire‑suppression zone, it rapidly vaporizes to extinguish the fire, offering excellent properties such as cleanliness, high efficiency, and environmental friendliness, making it a highly favored alternative to halon‑125.

1. Safety Performance

The extinguishing concentration of perfluorohexanone is no higher than the concentration that elicits toxicological effects, offering a high level of safety and making it suitable for use in occupied spaces.

2. Notes on Use

The manufacturing process for perfluorohexanone fire suppression systems is highly demanding; when selecting and applying such systems, the following factors should be carefully considered:

(1) Hygroscopic corrosivity.

Perfluorohexanone is itself a non-corrosive, highly insulating, and readily volatile liquid; however, when it comes into contact with moisture, it undergoes hydrolysis, generating acidic byproducts that can corrode metallic components and seals. Experimental results indicate that the acidic products formed during the hydrolysis of perfluorohexanone significantly affect ferrous and copper alloys, as well as certain rubber and plastic parts. Consequently, stricter requirements are imposed on the filling process of perfluorohexanone, necessitating rigorous control of moisture levels in both the extinguishing agent and the filling procedure. Failure to do so may lead to corrosion of the inner walls of storage cylinders and the cylinder head valves, thereby reducing the reliability of perfluorohexanone fire‑extinguishing systems and potentially posing safety risks.

(2) The atomization design has stringent requirements.

Perfluorohexanone has a low design concentration for fire suppression—approximately 4.5% to 6%—and remains in liquid form under ambient temperature and pressure. Unlike other gaseous extinguishing agents, it does not spontaneously diffuse or penetrate; therefore, in total‑flooding systems, ensuring that this limited quantity of extinguishing agent rapidly atomizes and permeates the interior of protected objects—such as cabinets and electrical equipment—is a critical challenge. Inadequate atomization can compromise fire‑suppression effectiveness.

 

3. Application Prospects

Perfluorohexanone does not deplete the atmospheric ozone layer (ODP = 0) and has a low global warming potential (GWP = 1). It has been internationally recognized and widely adopted as a replacement for halon‑freezing agents such as heptafluoropropane (HFCs).

Some argue that, upon release, perfluorohexanone reacts with atmospheric moisture to form acidic byproducts, which could adversely affect sensitive equipment. In reality, however, when discharged as an aerosol, perfluorohexanone rapidly evaporates in the air and does not pose a threat to precision instruments. Moreover, under fire conditions, the hazards posed by combustion products far outweigh any potential impact from the extinguishing agent.

(3) High-pressure water mist fire suppression system.

Fine-water‑mist fire‑suppression systems use water as the extinguishing medium, employing specialized nozzles to generate fine water droplets under high pressure. Classified by operating pressure, these systems can be categorized into high‑pressure, medium‑pressure, and low‑pressure types. In certain applications, high‑pressure fine‑water‑mist systems can serve as a substitute for halon‑free fire‑suppression systems such as heptafluoropropane.

Fine-water‑mist fire‑extinguishing systems offer advantages such as high efficiency, environmental friendliness, minimal water‑damage, and broad applicability, making them a viable alternative to halon‑free clean agent systems. However, the issue of water‑related damage is inherent, and such systems are not suitable for precision equipment rooms with ultra‑clean‑room requirements.

Key Point 5: Ultra-fine dry powder cannot be regarded as a substitute for heptafluoropropane and should not be used in areas requiring gaseous fire suppression systems.

Ultra-fine dry powder fire suppression systems cannot serve as a substitute for heptafluoropropane fire suppression systems. The following explains why:

(1) The application of dry‑powder fire suppression lacks regulatory basis, and current standards do not support the use of dry‑powder fire‑extinguishing systems.

In accordance with the principle of adaptability within the fire‑protection technical standards system, the locations for installing fire‑protection facilities are determined by fire‑resistance‑related or specialized codes, while the design, construction, and acceptance requirements for such facilities are governed by system‑level technical standards. The Code for Fire Protection of Building Design (2018 Edition), GB 50016–2014, specifies the applicable areas for automatic fire‑extinguishing systems, including automatic sprinkler systems, gaseous extinguishing systems, and water‑mist extinguishing systems, but it does not explicitly define the application scope of dry‑powder extinguishing systems. Furthermore, the code states: “Where a space is very large and only certain equipment constitutes the primary fire hazard requiring fire‑extinguishing protection, or where only a small number of relatively confined areas within a building contain equipment that requires protection, localized protection may be provided for these high‑risk components using compact automatic fire‑extinguishing devices such as fire‑detection tubes, aerosol generators, or ultra‑fine dry powder systems, rather than deploying a full‑scale automatic fire‑extinguishing system to protect the entire space.” In other words, the Code for Fire Protection of Building Design clearly stipulates that ultra‑fine dry powder systems are limited to localized protection in small spaces and cannot serve as a substitute for large‑scale automatic fire‑extinguishing systems. Note: The Code for Design of Dry‑Powder Fire‑Extinguishing Systems, GB 50347, is classified as a system‑level technical standard and therefore cannot be used as the basis for selecting a system type.

In particular, dry‑powder fire‑extinguishing systems often fail to comply with Article 9.0.8 of the General Code for Fire Protection Facilities (GB 55036), making them liable to be deemed in violation of mandatory provisions.

(2) Dry powder fire suppression cannot ensure sufficient impregnation time, and thus fails to meet the requirements for fire extinguishing.

According to the Code for Design of Gaseous Fire‑Extinguishing Systems (GB 50370), protection zones such as telecommunications equipment rooms and computer rooms, as well as areas affected by solid‑surface fires, must meet specified immersion‑time requirements to ensure effective fire suppression and prevent reignition. In contrast, dry‑powder extinguishing systems employ a single‑pass discharge method; since dry‑powder agents are solid particulates that settle rapidly after release, it is difficult to maintain the required immersion time, thereby failing to provide adequate protective coverage.

(3) After discharge, dry powder fire suppression systems cannot be effectively cleaned, and residual powder can impair equipment operation.

After discharge, dry‑powder extinguishing systems leave a layer of powder on floors and equipment surfaces. When this powder accumulates inside equipment or in the gaps of electrical wires and cables, it is difficult to remove, impairing heat dissipation and, once it absorbs moisture, potentially creating additional safety hazards. Consequently, dry‑powder systems are particularly unsuitable for protecting electronic equipment.

(4) Dry powder fire suppression systems are not suitable for fires inside equipment.

Numerous experiments have demonstrated that dry‑powder fire‑extinguishing systems are ineffective for extinguishing fires inside equipment and in cable tunnels (ducts). The primary reason is that, after discharge, the dry powder settles rapidly and exhibits poor distribution, making it difficult to achieve an effective extinguishing concentration within equipment and in gaps between wires and cables, and failing to meet the required impregnation time.

Unlike gaseous fire suppressants, dry‑powder extinguishing agents are solid particulates; even ultrafine dry powders consist solely of solid particles with a particle size no greater than 15 μm. After discharge, dry powder tends to settle, exhibits poor dispersion, and is easily obstructed, making it difficult to achieve a uniform and consistent extinguishing concentration and impossible to meet the required impregnation time.

Therefore, dry‑powder fire‑extinguishing systems (equipment) should not be used in locations where internal equipment fires may occur, nor in areas prone to deep‑seated fires, and they are also unsuitable for use in cable trenches, cable tunnels, and similar environments.

(5) In summary, ultra-fine dry powder cannot be regarded as a substitute for heptafluoropropane and should not be used in facilities requiring gaseous fire suppression. See the special topic: Common Misconceptions | Dry Powder Fire Suppression Systems (Equipment).
 

Appendix: Understanding the Kigali Amendment at a Glance

The following content is quoted from the website of the Ministry of Ecology and Environment of the People’s Republic of China: