Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone, which contains both of those minerals) and is the main component of pearls and the shells of marine organisms, snails, and eggs.
An ordinary breath for a 70-kg adult is about 500ml of air. We call this the tidal volume. Since oxygen is 21% by volume of air, then the volume of oxygen inhaled is about 105ml. The density of pure oxygen at sea level is 1.43kg per cubic metre.
An adult human weighing about 70kg has a resting respiratory rate of 12 breaths a minute. 60 minutes in an hour, 24 hours in a day makes 17 820 breaths in a 24-hr period. During this time he will inhale about 8640 litres of air. If he is exercising his respiratory rate can easily double, so this figure could go much higher. But if you were looking for a ballpark figure, this will do.