Breath-holding time greater than 30 seconds is usually considered normal. There is no absolute correlation between the length of breath-holding time and lung function, and the length of breath-holding time has some relationship with whether or not exercise is performed. Breath-holding test is also known as breath-holding test, the subject takes a deep breath and holds it, and starts timing the time until the breath is taken, which is called breath-holding time, and it can be used to initially determine the lung function, lung capacity and lung reserve capacity, but it can not be used to diagnose the disease due to the influence of other factors. Breath-holding time of more than 30 seconds is considered normal for an untrained person, and can be up to about 3 minutes for a trained person, or longer for athletes and people who exercise regularly. A shortened breath-holding time in untrained people is a good indicator of reduced lung function, but a trained person may not necessarily hold his or her breath for less than 30 seconds despite having reduced lung function, so other tests are needed to determine the status of lung function. If you suspect that there is a problem with your lung function, you can consult with a respiratory clinic.