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.
A border services officer at the port of entry in Canada will determine how long you can stay in Canada. Most visitors are allowed a six-month stay from the day they entered Canada. If the officer authorizes a stay of less than six months, they will indicate in your passport the date by which you must leave Canada. If you want to stay longer than your authorized stay, you should apply for an extension at least 30 days before the authorized end of your stay.