Chronic cough:

A cough that you have had for eight weeks or longer is considered chronic. This is an important early symptom that tells you something is wrong with your respiratory system.

Shortness of breath:

It's not normal to experience shortness of breath that doesn't go away after exercising, or that you have after little or no exertion. Labored or difficult breathing—the feeling that it is hard to breathe in out—is also a warning sign.

Chronic mucus production:

Mucus, also called sputum or phlegm, is produced by the airways as a defense against infections or irritants. If your mucus production has lasted a month or longer, this could indicate lung disease.

Wheezing:

Noisy breathing or wheezing is a sign that something unusual is blocking your lungs' airways or making them too narrow.

Coughing up blood:

If you are coughing up blood, it may be coming from your lungs or upper respiratory tract. Wherever it's coming from, it signals a health problem.

Chronic chest pain:

Unexplained chest pain that lasts for a month or more—especially if it gets worse when you breathe in or cough—also is a warning sign.