Whilst in the act of triple penetration, each cock filled cavity seals every possible air path of entry or escape thus causing an immensely pleasurable (I said pleasurable bitch!) sensation for the female recipient, as her body becomes akin to a vaccuum sealed container. Also see, Tupperwhore.
Samantha was absolutely dying to become airtight; she really was. Elaine's airtightedness was the perfect environment for the long-term storage of my balls. "Plug Jessica's nose Jack! She's trying to cheat by breathing through her nose!!!"