RBC stands for red blood cell, which is also known as red blood cell and is the most numerous type of blood cell in the blood. Red blood cells contain hemoglobin, which is why blood is red in color. Hemoglobin binds to oxygen in the air, so red blood cells transport oxygen inhaled into the alveoli to the tissues through hemoglobin, and carbon dioxide produced by metabolism in the tissues is transported to the lungs through the hemoglobin of red blood cells and is expelled from the body. Hemoglobin is more likely to combine with carbon monoxide, and when the level of carbon monoxide in the air increases, it can cause carbon monoxide poisoning, commonly known as gas poisoning.