I can't answer your question but there's a thread that might contain valuable info:
🐵 GasMonkey Setup 🐵 [Nitrogen SCBA] Positive Pressure Self-Contained Breathing Apparatus **images have been edited to ensure anonymity** Front view Side view Back view Pressure gauge Lung Demand Valve and Mask Bluetooth pulse oximeter Cylinder attachment Cylinder's connection...
sanctioned-suicide.net
If your mask isn't fully airtight there's a risk of failure bc the goal with this method is to be totally out of Oxygen - that is what leads to death. If there's only a small hole it could lead to failure. Basic brain functions can be kept up with very little Oxygen - even at the risk that we end up as veggies - our brains can't comprehend this - survival at any costs is how our brains work (from an evolutionary POV).