What is a common sign of a malfunctioning fire extinguisher?

A damaged pressure gauge or visible corrosion is indeed a common sign of a malfunctioning fire extinguisher. The pressure gauge plays a crucial role in indicating whether the extinguisher is charged and ready for use. If the gauge shows a reading outside the green zone, it may suggest that the extinguisher is either over-pressurized or under-pressurized, both of which can render it ineffective during an emergency. Additionally, visible corrosion can compromise the structural integrity of the extinguisher, leading to leaks or ruptures that could prevent it from functioning properly.

In contrast, options indicating full weight measurement, a new color marker on the label, or an intact plastic casing do not necessarily relate to the operational readiness of a fire extinguisher. Full weight could mean it is still charged, but it alone does not confirm whether all components are functioning correctly. A new color marker might suggest a recent inspection or maintenance, but does not indicate the condition of the extinguisher. Having an intact plastic casing is a good sign, but it does not account for internal mechanisms or the pressure status that are critical for its operational safety.