Gas fire extinguishing system is one of the most common fire extinguishing means in the market. It is often used in major shopping malls, workshops, power distribution rooms, libraries, archives and other places. Its excellent fire extinguishing performance is widely praised and widely used in the market. At the same time, gas fire extinguishing systems are also divided into many types: heptafluoropropane, IG541, ultra-fine dry powder, hot aerosol, etc.
Of course, many matters need to be paid attention to when using gas fire extinguishing products. Improper use will bring many unnecessary losses.
Today, I want to talk about the concentration range that needs to be noticed before using gas to extinguish the fire. How to design and the consequences of exceeding the standard.
The scheme design of gas fire extinguishing system is calculated according to the size of the protection area. Some people who do not understand or are unprofessional do not take the design concentration into account in the design drawings, especially the design dosage of heptafluoropropane fire extinguishing system, which is easy to be ignored. If it exceeds the standard, the consequences will be serious.
Parameters of gas fire extinguishing system
Code for design of gas fire extinguishing systems gb50370, NOAEL and LOAEL are explained as follows:
Non toxic reaction concentration
A large concentration of fire extinguishing agent that produces physiological reaction due to the toxicity of fire extinguishing agent is not observed.
Toxic reaction concentration (LOAEL concentration)
It can be observed that the concentration of fire extinguishing agent that produces physiological reaction due to the toxicity of fire extinguishing agent is small.
According to the definition, it is basically safe if the fire extinguishing design concentration in the protection area is below the NOAEL concentration. However, if the design concentration of the protection zone is above LOAEL, special attention needs to be paid. Exceeding the standard or not designing according to the specifications may have serious consequences. It can be toxic at first and life-threatening at worst.
According to code for design of gas fire extinguishing systems (gb50370), the concentrations of NOAEL and LOAEL of heptafluoropropane and IG541 are shown in the table below
Parameters of gas fire extinguishing system
It can be seen from the table that the LOAEL of heptafluoropropane fire extinguishing system is 10.5%. The design concentration of heptafluoropropane fire extinguishing agent should be 10% in the protection areas of books, archives, bills and cultural relics databases.
Code for design of gas fire extinguishing systems gb50370:
3.3.3 the design concentration of fire extinguishing in protective areas such as books, archives, bills and cultural relics databases should be 10%.
3.3.4 the fire extinguishing design concentration should be 9% in the protection areas such as oil immersed transformer room, distribution room with oil switch and self-contained generator room.
3.3.5 in the protection areas such as communication machine room and electronic computer room, the fire extinguishing design concentration should be 8%.
3.3.6 the concentration actually applied in the protection area shall not be greater than 1.1 times the design concentration of fire extinguishing.
Many people tend to ignore the limit of LOAEL concentration of heptafluoropropane when designing protection areas for books, archives, bills and cultural relics databases. In the design, the actual concentration in the protection area accidentally exceeds 10.5%.
6.0.7 the fire extinguishing design concentration or actual use concentration in the manned work protection area shall not be greater than the toxic reaction concentration (LOAEL concentration), which shall comply with the provisions of appendix g of this specification.
Therefore, special attention should be paid to this point in the design, especially when making the combined distribution system. In order to reconcile the dosage of chemicals in different protection areas, many designers only pay attention to the provisions: 3.3.6 the concentration actually applied in the protection area should not be greater than 1.1 times the design concentration of fire extinguishing.
Ignore the article: 6.0.7 the fire extinguishing design concentration or actual use concentration in the manned work protection area should not be greater than the toxic reaction concentration (LOAEL concentration), which should comply with the provisions of appendix g of this specification. This deserves the attention of designers.
The design and installation of gas fire extinguishing system need professional personnel, otherwise there will be trouble in the later stage, resulting in the consequences of not being able to extinguish the fire or endangering the safety of personnel, and the relevant responsible person will also bear the corresponding responsibility. It is suggested to find professional gas fire extinguishing system manufacturers to design.
