Green area: indicates that the pressure is normal and the fire extinguisher can be used normally;
Yellow area: indicates that the pressure in the fire extinguisher is too high and it can be used normally. But there is a danger of blasting and explosion.
Fire extinguisher is a portable fire extinguishing tool. Chemicals were put in the fire extinguisher to put out the fire. Fire extinguisher is one of the common fire prevention facilities. They are stored in public places or places where fires may occur. Different types of fire extinguishers contain different components and are specially designed for different fires.
Extended data:
1905, Professor Laurent of Russia invented a foam fire extinguishing agent in St. Petersburg. Aluminum sulfate is mixed with sodium bicarbonate solution, and stabilizer is added. Foam containing carbon dioxide produced after spraying floats on burning oil, paint or gasoline, which can effectively isolate oxygen and suffocate the flame.
1909, Davidson of new york obtained a patent. He used carbon dioxide to squeeze carbon tetrachloride out of a fire extinguisher, and this liquid immediately turned into a heavier nonflammable gas to extinguish the flame. Since then, small fire extinguishers such as dry powder fire extinguishers and liquid carbon dioxide fire extinguishers have appeared.
In ancient times, fire fighting equipment was very simple, nothing more than hooks, axes, shovels, buckets and the like. The first real special fire extinguisher was invented by British captains Manby and Norfolk in 18 16. This is just one or two barrels filled with 1 water and compressed air.
References:
Fire extinguisher-Baidu Encyclopedia