[Bernica]

Originally Posted by jwd

If you're talking about a dry chemical extinguisher, every year you should turn it upside down and tap the bottom with a rubber mallet until you can feel the powder break loose. In storage, the powder tends to cake up at the bottom so when you try to use it, the only thing that comes out is the nitrogen propellant.
Also, lightly tap the gauge with your finger to make sure the needle isn't stuck. If it still reads charged, you're good to go.

Good to know and thanks!