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.
According to the Government of Canada Visa and Immigration Department, most visitors who enter Canada are authorized to stay for up to six months with only a passport. To extend a stay, the visitor must apply for a visa 30 days prior to the departure date that was established when the visitor first entered Canada.