Given the task definition and input, reply with output. In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant. 

The human body takes a breath inward. Air is transported to the lungs. Air reaches the alveoli, the smallest air sacs in the lungs. In the alveoli, air passes into the blood within small capillaries. The gaseous oxygen in the air dissolves into the capillary blood. The dissolved oxygen is picked-up by red blood cells. The red blood cells bind the oxygen via a protein called heme. Red blood cells circulate throughout the body and reach the various tissues. Within small capillaries, the heme release the oxygen. The oxygen can then reach the cells within the tissue. 

air ,oxygen ,red blood cells 