The fire extinguisher pressure gauge is used to indicate the pressure inside an extinguisher. This pressure can fluctuate depending on the temperature of the extinguisher. Below is an explanation of the different lines on the gauge.
Gauges manufactured to EN3 show three lines:
The left hand line (1) indicates the lowest pressure at the minimum operating temperature permissible
The middle line (2) indicates the pressure at a temperature of + 20?C (room temperature)
The right hand line (3) indicates the maximum pressure at the maximum operating temperature permissible
As long as the needle is within the green area between line 1 and 3, the extinguisher is safe to use. Depending on the type of extinguisher the lines on the gauge represent different operating temperatures. For a powder extinguisher the gauge represents the following: