Into the air why does krakauer feels better after harris turns the valve on the regulater?

In "Into Thin Air," Jon Krakauer feels a sense of relief and improved comfort after Harris turns the valve on the regulator because it allows for a better flow of oxygen. This increase in oxygen supply alleviates some of the physical and mental strain he is experiencing at high altitudes, where oxygen levels are significantly reduced. The immediate boost in oxygen helps him regain clarity and feel more stable in the challenging conditions of the climb.