At what cabin pressure altitude must aircrew use supplemental oxygen?

The requirement for aircrew to use supplemental oxygen at 10,000 feet MSL is rooted in physiological responses to reduced atmospheric pressure. At altitudes of 10,000 feet and above, the partial pressure of oxygen decreases, leading to a reduction in the amount of oxygen available for bodily functions.

For aircrew, using supplemental oxygen begins at 10,000 feet MSL to ensure that they maintain adequate oxygen levels in their blood, which is essential for cognitive functions, physical performance, and overall safety during flight operations. This altitude is a threshold established based on aviation safety protocols that aim to minimize the risks associated with hypoxia.

Higher altitudes, such as 12,000 and 14,000 feet, also require supplemental oxygen, but the critical point for initial supplementary use begins at 10,000 feet MSL. Hence, this altitude is significant as it marks the transition to a mandatory need for supplemental oxygen in order to safeguard aircrew health and operational effectiveness.