• activity: number of disintegration per second or decays per second. Both the number of atoms and the activity follow an exponential decay law.
• AEC: Atomic Energy Commission.
• aerosol: a system of solid or liquid particles which are dispersed in a gaseous medium and are suspended in the medium for a relatively long time compared to the time scale of interest. air exchange ration: the rate at which fresh air entering a home replaces the existing air supply.
• alpha particle: particle emitted in the decay of some radioactive nuclei; a nucleus of the helium isotope of mass 4.
• alveoli: the small sacs in the lung where gases are exchanged with the bloodstream.
• atom: fundamental particle of matter consisting of at least one proton and zero or more neutrons surrounded by an electron cloud equal to the number of protons.
• attached fraction: the fraction of a set of radon daughters adsorbed onto or absorbed into the aerosol particles.
• becquerel (Bq): S.I. unit of radioactive decay; 1 Bq = 1 disintegration per second.
• Beta particle: an electron with a positive or negative charge emitted in the decay of some radioactive nuclei.
• BPA: Bonneville Power Administration, an agency of the D.O.E. which oversees the sale of electric power generated by dams in the Pacific Northwest.
• charcoal canister: radon measurement device that absorbs dust and radon.
• cilia: hair like projections of some cells of the bronchial walls, which move in such a way as to help the elimination of particulate matter via the muco-ciliary escalator.
• curie: unit of radioactive decay; 1 Ci = 37,000,000,000 disintegration per second.