Help What does it mean to have exit bag be loose or 2 fingers and not too tight around neck area?

[ocean2200reef]

Hello I would like to use an exit bag but am not understanding the whole thing about leaving 2 fingers space or not making it tight, wouldn't curb fail because there will be air coming in and it won't be full nitrogen then?

 

[locked*n*loaded]

The "2 finger" space is to allow the CO2 you exhale to be pushed out of the bag, so that a hypercapnic response isn't triggered. The elastic is not supposed to fit tight around your neck. You should read the inert gas megathread in the "stickies" here, and there are youtube vids on how to make a bag, or at least used to be.

 

[Aprilwithcake]

the gas will push the air out as it fills pushing the co2 away.