how to make an exit bag

[WhoIsSolace]

i have an oven bag and plan to use some tubing from an oxeygen mask set, the tank is gonna be 99.5 nitrogen and im unsure what the other. 5 percent is but im assuming it won't be an issue. is this everything i need am i missing something, im mainly worried about gas leaking from the bag or not having enough to last until im gone. does tge bag need to be sealed do i shut off the gas once its inflated. idk if these are silly worrys i jus want this to work.