I have a question in regards to ansul sentry fire extinguishers. I have a a02xx fire extinguisher that I replaced with a newer one this one isnt bad it was holding just fine and I emptied out the baking soda (not actual baking soda it was really fine powder)

The gauges on the side of the handle, are they always pressurized, like if I were to unscrew it while the extinguisher still has pressure, will it start to lose pressure without squeezing the handle?