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.
Oxygen makes up 21% of the air around us. In exhaled air, this reduces to 15% in exhaled air. Each breath exchanges a volume of 500ml of air between our lungs and the surroundings, known as the tidal volume. So, a reduction of 6% of oxygen means that we consume 30ml of oxygen per breath. Normal breathing rate is at 12breath/min, corresponding to an oxygen consumption of 360ml/min.