It is not used in China. The domestic standard does not have this rigid requirement, but abroad, especially in the United States and Europe, double-layer protection is required.
To put it bluntly: in China. In China, equipment is more valuable than people. Gas fire extinguishing is a one-time extinguishing. If it doesn't work, people still have to go in and put out the fire.
Abroad, people. are more valuable than equipment. Their purpose is that the person who started the fire must leave the premises and is not allowed to put out the fire on their own.
If they cannot put out the fire. turned off, immediately start the water jet. We would rather have equipment damaged than suffer losses.