CT-Rich
Contributor
15' is absolutely the most dangerous depths to do it at. You would be far safer trying it from 60 to 40'. The change in volume is the last 15'. The reason it is so dangerous (in my understanding) is that your lungs aren't designed to feel pain. You can't feel an over expansion injury, so you may not know you have just killed yourself until after you have done it.I recall being taught to CESA properly in the classroom.
Dont recall practicing it. Did that myself. Starting easy, 15' up to my safety stop.
If you want to take the risk and try it out, there are no scuba police. But students should not be expected to try a skill that could unintentionally lead to their death if not done correctly.