Dirt in sputum like dust is clinically common in diseases of the respiratory system. For example, acute upper respiratory tract infections, acute attacks of chronic pharyngitis, chronic nasopharyngitis, bronchitis, pneumonia, etc. are common. Due to many inflammatory secretions in the airways, airborne dust is inhaled and deposited in the sputum, and the symptoms of having dirt in the sputum are manifested. It can be seen in infection by many pathogens, such as septic bacteria, mycoplasma, chlamydia, rickettsia, special pathogenic infections such as Mycobacterium tuberculosis, etc. If necessary, sputum can be taken for pathogen culture for clear diagnosis and timely treatment.