Where does the greatest change in atmospheric pressure occur, measured in mmHg?

The greatest change in atmospheric pressure occurs in the first 10,000 feet of altitude. This is due to the fact that the majority of the Earth's atmosphere is concentrated within the lower altitudes. As altitude increases, the density of the air decreases, leading to a more rapid change in pressure in those initial layers.

Specifically, within the first several thousand feet, there is a significant drop in pressure, measured in mmHg, due to the exponential relationship between altitude and atmospheric pressure. This rapid decrease continues to moderate but is less pronounced above 10,000 feet. In fact, while the pressure changes, they occur at a much slower rate as you climb higher in the atmosphere, which is why the most dramatic shifts are noted within that first 10,000 feet of ascent. This principle is essential for pilots to understand, as it influences aircraft performance and altimeter settings.