A spirometer may also be used to measure pulmonary function. A spirometer is the main piece of equipment used for basic Pulmonary Function Tests (PFTs). An incentive spirometer is often used as part of the breathing exercises. However, his spirometer could measure only volume, not airflow. A spirometer measures ventilation, the movement of air into and out of the lungs. This spirometer is specially designed to improve one's lung function. This spirometer measures the flow rate of gases by detecting pressure differences across fine mesh. Physiological chemistry occupied much of his attention and he developed an early spirometer. A person's vital capacity can be measured by a wet or regular spirometer. South African studies also utilized the spirometer to address racial and class differences.