Clean agent selection: Performance, human safety and environmental considerations
In this article we compare the performance, environmental impact and human safety of the clean fire protection agents. The impact of the Kigali Amendment on Middle East markets is also detailed.
Inert Gas Agents. The inert gas agents cannot be compressed to liquids and can only be stored as high pressure gases. As a result, inert gas extinguishing systems require the use of high pressure storage cylinders. Inert gas systems also require a much larger number of cylinders and much more storage space compared to the other clean agents, further adding to the cost of inert gas systems.
In addition to the substantial weight and volume penalties associated with inert gas agents, acoustical damage to hard disk drives (HDDs) during inert gas agent discharges is well documented1,2. Special “silencing” nozzles have been designed in attempts to mitigate this problem, but it is not possible to design a nozzle that will prevent HDD damage in all scenarios, as the impact of an inert gas discharge on HDD performance is dependent upon structural details and the sound absorbing characteristics of objects within the structure.
The halocarbon clean agents can be stored as liquefied compressed gases, and require fewer cylinders and less storage space compared to the inert gas agents., In addition, their use does not require high pressure cylinders or piping. To date there have been no instances of acoustical damage to hard disk drives associated with the discharge of the HFC clean agents.
Clean agent system design comparison
Due to its high boiling point, uniform distribution of Novec 1230 throughout an enclosure is more difficult to achieve compared to the case of low boiling agents such as FM-200 or the inert gas agents. This difficulty in achieving uniform distribution is reflected in the relatively low nozzle area coverages provided by Novec 1230 systems seen in Table 1. Inert gas systems also tend to have lower maximum nozzle area coverages: for example, FM-200 systems can achieve maximum nozzle area coverages of almost four times that of Inergen systems.
Decreased nozzle area coverage leads to an increase in system cost due to the requirement of additional nozzles and piping. Table 2 compares the case of a 38 m x 38 m x 3 m (4332 m3) IT facility. In addition to requiring 25% more Novec 1230 by mass, four times the number of nozzles are required for protection with Novec 1230 compared to protection with FM-200. Table 2 also demonstrates the large weight and volume penalties associated with inert gases.
Ozone depletion and global warming
The Halons are ozone depleting substances (ODSs) and were eliminated in most fire protection applications due to their large contribution to ozone depletion.
Inert gas and halocarbon clean agents do not contribute to stratospheric ozone destruction. Environmental concerns in this case include global warming and ground level smog formation. The inert gas products contribute to neither. Perfluoroketones, due to their high chemical reactivity, are classified as volatile organic compounds (VOCs), and contribute to ground-level smog formation.
Emissions of HFCs from fire suppression applications are extremely low, hence the impact of these emissions on global warming is negligible. US EPA data3 indicate that the impact on global warming of HFCs in fire protection represents only 0.02% of the impact of all GHGs on global warming. Figure 1 compares the environmental impact of Halons to that of HFCs in fire protection, and explains why whereas the Halons were banned, there are no proposals for the banning of HFCs in fire protection, as their contribution to global warming is negligible. Fully 38% of ozone depletion was attributed to Halons, compared to 0.02% of global warming attributed to HFCs in fire protection.
The Kigali Amendment to the Montreal Protocol (MP) adds HFCs to the list of substances to be phased down under the MP. Details of the HFC allocation schedule for Middle Eastern countries are provided in Table 3.
The Kigali Amendment does not call for a complete phase-out of HFCs, but a phase-down to 15% of the baseline by 2047. This remaining production extends out indefinitely, a recognition of the importance of HFC use in many critical and non-emissive applications, such as fire protection. The phasedown begins more than a decade from today – in 2028 – at which point consumption will be frozen to baseline levels achieved in 2024 to 2026.
The Kigali Amendment does not inhibit or limit the sale of HFCs into the fire suppression market. The allocation scheme represents a “cap and reduction” of HFCs on a GWP-weighted basis over a specific time period – a “phase-down,” NOT a “phase- out” of HFCs.
Figure 2 provides a representation of the Kigali Amendment allocation/phase-down scheme as it applies to Group 2 Article 5 Parties. Also shown for reference in Figure 2,is the relative size, on a GWP-weighted basis, of the worldwide HFC market4. As can be seen from Figure 2, HFCs in fire protection represent only 3% of the total HFC market on a GWP-weighted basis.
The HFC phase-down, as stipulated by the Kigali Amendment leaves 15% of the 2024-2026 HFC baseline available indefinitely, which is more than adequate to encompass the needs for fire protection in the Middle East. HFCs in refrigeration, foam blowing and aerosol propellant applications account for almost the entire global HFC market. In the future the allocations required for these markets will be only a fraction of what is required today, due to the replacement of HFCs in refrigeration, propellants and foam expansion. The need for HFC refrigerant allocations is already decreasing as the mobile air conditioning industry migrates from HFC-134a based to HFO-1234yf based technologies: an estimated 50 million cars will employ HFO-1234yf globally by year end 2017. The need for HFC foams and aerosols is decreasing as these industries have begun migrating from HFC to HFO-based technologies. Additional regulatory constraints on specific HFCs in refrigeration and other non-fire protection applications, along with the shrinking requirements of the non-fire protection markets, will result in additional allowances for HFCs used in fire protection. The 15% remaining GWP-allocations will be available throughout the course of the phasedown to support the requirements of key applications such as fire protection to protect the Middle East’s infrastructures and crucial facilities for decades to come.
Humans make up an important part of the environment, and any environmental evaluation should include consideration of the interaction of a released substance with humans. As seen, for example, in the increasing concern over the effects of genetically modified organisms (GMOs), the public is becoming increasingly concerned with any substance that can react within the human body. Inert gas and HFC clean agents are not chemically reactive and do not react in the human body. The perfluoroketone Novec 1230 reacts with water in the lungs to produce perfluoropropionic acid, a strong, corrosive and toxic acid.
Table 4 provides a summary comparison of the clean agents in terms of desired properties.
As can be seen from Table 5, the HFCs, followed by the inert gases, provide the best overall combination of the properties desired in a clean agent. This can also be seen in the clean agent market: the most widely employed clean agent worldwide is the HFC agent FM-200, followed by the inert gas agent Inergen.
For more information, go to FM200.com
- K. Green, et. al., Clean Agent Fire Suppression and Hard Disk Drives, 2013.
- B. Rawson, et. al., Inert gas data center fire protection and hard disk drive damage (2012).
- US EPA Report 430-P-17-001 (2017).
- UNEP Fact Sheet 2, 2015.