Fire extinguishers must be inspected monthly by lab personnel.  The reverse side of the tag should contain an area for this monthly check to be documented.  Checks include physical condition of the fire extinguisher (i.e. no visible damage to cylinder or hose); presence of the pin in the handle; a plastic tab that has not been broken (indicating that It’s been discharged); and finally, a check of the gauge (if present) to verify it is not over- or under-charged.