Fire extinguisher pressure gauge?

Now, many owners are equipped with vehicle fire extinguisher, that how do you know a fire extinguisher pressure gauge? Fire extinguisher pressure gauge is divided into three sections: the first paragraph is red area, pointer refers to the red area, said in dry powder fire extinguishers pressure is small, can't, have failed. Regular fire equipment store at this time should be to filling powder again. The second section ( A narrow) Is green zone, a pointer to point to in the area, said the pressure is normal, can be normal use. The third section of the yellow area, said the powder pressure inside the fire extinguisher is too big, can spray powder, but is in danger of blasting, explosion. Such a state of fire extinguisher, also should get regular back filling dry powder fire equipment store. Huang Ge area is in the process of production and maintenance of fire extinguishers for manufacturer use aeration zone, under normal circumstances, the normal manufacturer will fill in the green zone, if the pointer appears in Huang Ge area indicates the pressure is too large, as it says there is a certain risk, but it doesn't mean the invalid when using.