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.
Another 180 days and another â Canadians can get into trouble if they routinely spend substantially more than 180/365 days in the US (e.g., 240 days). Typically these Canadians will leave the US for a few days or weeks and then return as visitors, thinking that they have âreset the counterâ to 180 days. Not so.