Due to the different physique of each person, it is difficult to specify the exact time to get lung cancer from inhaling asbestos fibers without wearing a mask, which generally varies from person to person. Asbestos is a carcinogen recognized by the World Health Organization, and when patients are exposed to asbestos for a long period of time, it may increase the risk of cancer, but it is not a certainty that exposure to asbestos will lead to lung cancer. Lung cancer belongs to primary malignant tumors of the lungs, and its development may be related to a variety of factors such as genetic predisposition, smoking, occupational exposure, air pollution and diet. Due to the different physique of each person and different living environment, it is usually difficult to specify the specific time of lung cancer when asbestos fibers are inhaled without mask. If someone in the patient’s family suffers from lung cancer, and the patient also has smoking, improper diet and other bad habits, lung cancer may develop within 3-5 years after prolonged inhalation of asbestos. If the patient is healthy and has no family history or other bad habits, his/her development period may be longer, and the exact time varies from person to person. People who have been exposed to asbestos fibers for a long time are advised to wear masks and have regular medical check-ups.