Helium-3 of the airway tree, locate unventilated defects, measure the alveolar oxygen partial pressure, and measure the ventilation/perfusion ratio. This technique may be critical for the diagnosis and treatment management of chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD), emphysema, cystic fibrosis, and asthma. Production, sales and distribution of helium-3 in the United States are managed by the US Department of Energy (DOE) Isotope Program. Virtually all helium-3 used in industry today is produced from the radioactive decay of tritium. Tritium is a radioactive isotope of hydrogen and is typically produced by bombarding lithium-6 with neutrons in a nuclear
Tritium radioluminescence region of the body, again due to the low penetration depth. The biological half-life of tritium—the time it takes for half of an ingested dose to be expelled from the body—is low, at only 12 days. Tritium excretion can be accelerated further by increasing water intake to 3–4 liters/day. Direct, short-term exposure to small amounts of tritium is mostly harmless. If a tritium tube breaks, one should leave the area and allow the gas to diffuse into the air. Tritium exists naturally in the environment, but in very small quantities. Because tritium is used in boosted fission weapons and thermonuclear