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.
For example, if a visitor's passport is set to expire prior to six months, the visitor will be required to leave early. The actual date of departure will be noted beside the entry stamp or in a separate document. You can usually stay in Canada without a visa for six months. If you plan to stay longer, understand the procedures that you must go through to enter the country and apply for a visa. Make sure your passport is valid for the length of your visit, and be prepared for changes the immigration officer may require.