What is the rule of thumb for oxygen usage at altitude?

The guideline for oxygen usage at altitude is primarily aimed at preventing hypoxia, which is a deficiency in the amount of oxygen reaching the tissues. As altitude increases, the partial pressure of oxygen decreases, which can lead to difficulty in maintaining adequate oxygenation.

Using supplemental oxygen above 10,000 feet is particularly important because, at this altitude, the risks of hypoxia become more pronounced. Most individuals may start to experience symptoms of hypoxia at this level, which can impair cognitive function, judgment, and coordination, critical aspects for anyone operating in an aerospace environment. The use of supplemental oxygen helps mitigate these risks by ensuring that sufficient oxygen is available to maintain normal physiological function.

At altitudes lower than 10,000 feet, healthy individuals may typically acclimatize without the need for additional oxygen; however, factors such as individual health conditions, duration of exposure, and activity level can influence the need for supplemental oxygen even at these lower altitudes. As a general practice for safety, especially in aerospace operations, the recommendation is to use oxygen above the 10,000-feet threshold to proactively combat potential hypoxic effects.