What do the three colors (red, green, and yellow) on the fire extinguisher mean?

Red area: Indicates that the dry powder pressure in the fire extinguisher is low and may not be ejected or has expired;

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 can be used normally. But there is a risk of blasting and explosion.

A fire extinguisher is a portable fire extinguishing tool. Chemicals are placed in fire extinguishers to put out fires. Fire extinguishers are 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 ingredients and are designed for different causes of fires.

Extended information:

In 1905, Professor Laurent of Russia invented a foam fire extinguishing agent in St. Petersburg. He mixed aluminum sulfate and sodium bicarbonate solution and added a stabilizer. After being released, foam containing carbon dioxide is generated and floats on the burning oil, paint or gasoline, which can effectively isolate oxygen and suffocate the flame.

In 1909, Davidson of New York obtained a patent for using carbon dioxide to press out carbon tetrachloride from a fire extinguisher. The liquid would immediately turn into a non-flammable heavier gas to suffocate the flame. Since then, dry powder fire extinguishers, liquid carbon dioxide fire extinguishers and other small fire extinguishers have appeared.

The fire extinguishing equipment in ancient times was very simple, nothing more than hooks, axes, shovels, buckets and the like. The first truly dedicated fire extinguisher was invented by Manby, a British captain and Norfolk native, in 1816. It was just one or two barrels filled with more than 1 liter of water and filled with compressed air.

Reference: Fire extinguisher-Baidu Encyclopedia