How long does it take for the lungs to get rid of carbon dioxide?

Air enters through the nose or mouth, this air then travels down the wind pipe, past the voice box and to the lungs. The lungs divide into two small tubes called bronchi, these bronchi then split into thousands of tiny tubes called bronchioles, at the end of these tiny bronchioles are millions of small 'air sacs' called alveoli. Once in the alvoli gas exchange of carbon dioxide and oxygen in the capillary walls happens.

The oxygen which you have breathed in through your nose or mouth is diffused through the capillary walls to meet red blood cells, which then take the oxygen to the heart, where it pumps the blood cells to cells all over the body that need oxygen to function and do its job correctly.

when this oxygen reaches the cells it kind of 'swaps' positions with the carbon dioxide (CO2) which has been created as a waste product by the body's cells.

Once the CO2 is attached to the blood cells, it is returned to the heart where it pumps the blood cells back to the lungs, where gas is diffused again and the cycle starts again.

sorry, a bit confusing.