How should you check the Lav Fire Extinguisher for the ERJ?

Using the O2 tool to verify the green zone is the correct approach when checking the Lav Fire Extinguisher for the ERJ. This tool provides a reliable method for ensuring that the pressure within the extinguisher is at an appropriate level, as indicated by the green zone. Proper maintenance and checks of fire extinguishers are crucial for safety during emergencies, and the O2 tool is designed specifically for this purpose to give a clear and immediate reading on the extinguisher's readiness.

While other methods, such as checking the manual pressure gauge or inspecting the hose for cracks, may seem logical, they do not provide the same level of ease and immediacy as the O2 tool. Additionally, simply checking the color of the extinguisher label does not guarantee the functionality or pressure status of the extinguisher, making it a less effective option for ensuring readiness.