No. Just take a few natural breaths in out in out in out and then hold your breath on that last out. Your bolt score is how long you can hold it before the first urge to breathe. it’s obviously not a clinical test, but typically it’s a pretty good indicator of how well you tolerate CO2. For perspective, my first urge to breathe is between four and six seconds and I can’t hold that exhale for more than 15 seconds total. And the crazy thing is, I can hold an inhale for over three minutes.