In gas fire suppression systems, it's essential to know the design concentration range—exceeding it can lead to severe consequences!

　　Gas fire suppression systems are one of the most common firefighting methods available on the market, frequently used in various settings such as large shopping malls, industrial plants, electrical distribution rooms, libraries, and archives. Their outstanding fire-extinguishing performance has earned widespread acclaim and broad application across industries. At the same time, gas fire suppression systems come in several different types, including heptafluoropropane, IG541, ultra-fine dry powder, and aerosol-based systems.

　　Of course, there are many precautions to keep in mind when using gas-based fire suppression products—improper use can lead to numerous unnecessary losses.

　　Today, we'll discuss the concentration ranges you need to consider before using gas-based fire suppression—and how to design systems properly, as well as the consequences of exceeding those limits.

　　The design of gas fire suppression systems is calculated based on the size of the protected area. Unfortunately, some individuals who lack expertise or are not professionals fail to account for the design concentration when creating their drawings—particularly when it comes to the design dosage for heptafluoropropane fire suppression systems, which is easily overlooked. However, exceeding the prescribed limits can lead to severe consequences.

　　Gas Fire Suppression System Parameters

　　"Code for Design of Gaseous Fire-Extinguishing Systems" GB50370 provides the following explanations for NOAEL and LOAEL:

　　No-Observed-Adverse-Effect Level Concentration (NOAEL Concentration)

　　No physiological reactions were observed from the relatively high concentrations of the extinguishing agent, likely due to its toxicity.

　　Toxicity Reaction Concentration (LOAEL Concentration) LOAEL Concentration

　　It is possible to observe physiological responses caused by the toxicity of fire extinguishing agents at relatively low concentrations.

　　By definition, if the fire suppression design concentration in a protected area is below the NOAEL level, it is generally considered safe. However, if the design concentration in the protected area exceeds the LOAEL level, special attention is required, as surpassing these thresholds—or failing to follow proper design guidelines—could lead to severe consequences. At best, this may result in poisoning; at worst, it could even threaten life itself.

　　According to the "Code for Design of Gas Fire-extinguishing Systems" GB50370, the NOAEL and LOAEL concentrations for Heptafluoropropane and IG541 are shown in the following table.

　　Gas Fire Suppression System Parameters

　　As shown in the table, the LOAEL for the heptafluoropropane fire suppression system is 10.5%. Meanwhile, when using heptafluoropropane extinguishing agents to protect areas such as libraries, archives, document repositories, and cultural heritage storage facilities, the recommended design concentration for fire suppression should be 10%.

　　Article of GB50370, "Code for Design of Gas Fire-extinguishing Systems":

　　3.3.3 For protection zones such as libraries, archives, document repositories, and cultural relic storage facilities, the recommended fire suppression design concentration should be 10%.

　　3.3.4 For protected areas such as oil-immersed transformer rooms, switchgear rooms equipped with oil-filled switches, and auxiliary generator rooms, the recommended fire suppression design concentration should be 9%.

　　3.3.5 For protected areas such as communication equipment rooms and electronic computer rooms, the recommended design concentration for fire suppression should be 8%.

　　3.3.6 The concentration actually used in the protected area should not exceed 1.1 times the fire suppression design concentration.

　　Many people tend to overlook the LOAEL concentration limit of heptafluoropropane when designing protective zones such as those for books, archives, documents, and cultural heritage repositories. As a result, the actual concentration in the protected area can inadvertently exceed 10.5% during the design process.

　　6.0.7 The design concentration or actual use concentration of fire suppression agents in protected areas shall not exceed the concentration causing toxic reactions (LOAEL concentration), which must comply with the provisions of Appendix G to this standard.

　　Therefore, special attention must be paid to this point during the design process—especially when developing a combined distribution system. To balance the amount of extinguishing agent required across different protected zones, many designers focus solely on Article 3.3.6: "The actual concentration applied in a protected zone should not exceed 1.1 times the fire suppression design concentration."

　　However, clause 6.0.7 states that the design concentration or actual usage concentration of fire suppression agents in occupied protection zones should not exceed the concentration associated with toxicological effects (LOAEL), as specified in Appendix G of this standard. This is an important consideration for designers to keep in mind.

　　The design and installation of gas fire suppression systems must be handled by professionals; otherwise, problems may arise later, potentially leading to failure to extinguish fires or even endangering personnel safety. In such cases, the individuals responsible will also bear the corresponding liabilities. It is recommended to consult a professional gas fire suppression system manufacturer for expert design services.