A pulmonary nodule is a discrete opacity in the lung which may be caused by: 1  Neoplasm: benign or malignant. 2  Granuloma: tuberculosis. 3  Infection: roundish pneumonia. 4  Vascular: infarct, varix, granulomatosis with polyangiitis, rheumatoid arthritis.
1 Helium is also commonly used to pressurize and purge systems of unwanted gases. 2  It is also used in controlled atmospheres when the levels of different gases have to be kept constant. 3  It is used as a protective gas when growing silicon and germanium crystals and when producing titanium and zirconium.
eries, and other industrial facilities use nitrogen gas to purge equipment, tanks, and pipelines of vapors and gases. Nitrogen gas is also used to maintain an inert and protective atmosphere in tanks storing flammable liquids or air-sensi-tive materials. It may be delivered in cylinders or tanks, or generated onsite (Figure 1). Liquid nitrogen is used in a variety of applications, particularly in the food and pharmaceutical industries, to