When is liquid oxygen (LOX) considered empty?

Liquid oxygen (LOX) is considered empty when the gauge reads at 10%. This is a critical measurement for ensuring safety and operational readiness in aviation environments where LOX is used. The 10% mark indicates that there is enough liquid oxygen remaining to be functional but not enough for extended use, prompting crews to plan for refueling to avoid being caught with insufficient resources. Understanding this threshold helps in maintaining the necessary oxygen supply for pilots during high-altitude flights, where supplemental oxygen is essential for safety and performance.

While other percentage markers are relevant for gauging levels, they do not reflect the critical point at which the oxygen is deemed no longer usable, reinforcing why the 10% gauge reading specifically designates the LOX as empty.