It is not recommended to hold your breath to measure lung capacity. Lung capacity is the amount of gas that can be exhaled after a single hard inhalation. Normal values for spirometry are about 3500 to 4000 ml for adult men and 2500 to 3000 ml for adult women. spirometry is an indicator of the body’s ability to take in oxygen and expel carbon dioxide, which decreases with age and the decline in the health of the lungs. Decreased spirometry indicates the presence of restrictive ventilatory dysfunction, which is commonly associated with reduced lung volume (lobectomy, atelectasis, pulmonary fibrosis, spondylolisthesis, pneumothorax, pneumonia, tuberculosis, pleural effusion, etc.). Decreased lung capacity is manifested by decreased exercise tolerance, inability to concentrate on work and study for a long period of time, shortness of breath and chest tightness after activities, and easy drowsiness. In case of decreased lung capacity, first of all, you should actively treat the cause of the disease and increase your lung capacity with appropriate exercise. If there is any discomfort, go to the hospital in time.