What characteristic of a fire extinguisher's gauge indicates it is in proper working condition?

The characteristic of a fire extinguisher's gauge that indicates it is in proper working condition is when it is in the green zone. This green area on the gauge signifies that the extinguisher is fully charged and ready for use in case of a fire emergency. Properly maintained fire extinguishers are crucial for safety, and the gauge provides a quick reference to determine whether the extinguisher will function effectively if needed. A gauge in the green zone assures personnel that the extinguisher has not been tampered with and is reliable for immediate action.