What is the required reading for the gauge of the POB during preflight?

The required reading for the gauge of the POB (Portable Oxygen Bottle) during preflight is 1500 psi or greater. This is critical because 1500 psi ensures that there is a sufficient amount of oxygen available for emergency situations, especially in an aircraft environment where supplemental oxygen may be needed due to altitude or in the event of cabin depressurization. Maintaining this minimum pressure level helps ensure the safety and readiness of the oxygen system for passengers and crew during a flight. Having lower pressures could compromise the effectiveness of the oxygen supply, potentially putting individuals at risk if an emergency arises. The specified threshold of 1500 psi is established based on safety standards and the operational requirements of the aircraft to ensure readiness in emergencies.