Gas exchange is the delivery of oxygen from the lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs. It occurs in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.
Admitted for 180 days â Canadians admitted in âVisitor for Pleasureâ or B-2 status without a B-2 visa in hand are deemed to be admitted for 180 days under current US Customs and Border Protection (CBP) interpretation of the rules.
In actual fact, the rule is that on any particular visit, a Canadian can stay in the United States for no longer than six months. However, a Canadian may very well be able to stay in the U.S. for longer than six months cumulative time in any given calendar year, provided they are not trying to live there permanently.