Background. Toxic substances may be inhaled or aspirated not always by patients themselves but sometimes by healthcare providers unintentionally by nasogastric administrations or medications. Aspirated toxic particles may cause injury in the pulmonary epithelium at various levels of the respiratory tract, leading to a spectrum varying from simple symptoms to severe chronic disease. Imaging features of substances are different depending on their structure and are not well known. Moreover, on follow-up, radiologic findings are not well correlated with clinical findings which progress or recover more rapidly.