# How does atmospheric pressure change with depth?

Atmospheric pressure DECREASES at altitude. Pressure INCREASES at ocean depth. And this is certainly an issue for scuba divers... At the surface they are breathing gas at $1 \cdot a t m$ pressure... At a depth of $10 \cdot m$ they breathe air at $2 \cdot a t m$...and at $20 \cdot m$ they breath at $3 \cdot a t m$. At higher concentrations, dinitrogen gas can have narcotic effects....and of course, rapid ascent by divers may lead to dissolved gas coming out of solution, a dangerous and potentially life-threatening situation.