Particles removal from radioactive gases

While the major removal of radon gas from air is by radioactive decay, the chemically radioactive decay products (formerly called radon daughters) may additionally be removed by processes such as washout and plating-out on surfaces. In air inside buildings, these radioactive decay products can attach themselves to walls, floors, people, or airborne particles that are inhaled into the Ivmgs. Unattached radon decay products can also be inhaled and, subsequently, can become deposited on the Ivmg tissue. As a consequence, radon decay products are seldom in radioactive equilibrium with radon in the lower atmosphere (near the earth s sruface) or indoors. 

Perron GA, Erbe F, Fiirst G, Haider B, Haller J, Kohl B, Kreyling WG, Schumann G, Stocker M, Heyder J. A scintillation counter for measuring removal of radioactive particles from dog lungs. J Aerosol Sci 1989 20 1297-1300. 

Pathways for venting the containment atmosphere may be provided for a number of reasons, and these pathways may be equipped with filters to remove iodine from the vented gas. Filters for iodine removal can be present in both passive systems (in which flow continues only as long as there is a pressme difference) and active systems (in which there is a continuous forced flow at a controllable rate). Dry filters intended for the removal of aerosol particles are not likely to be effective for the removal of gaseous forms of iodine, especially organic iodides. Even if gaseous iodine will absorb on the filter mediiun, heat loads on the filter medium caused by radioactive decay can lead to revaporization of the absorbed iodine. Filters that involve water must be maintained at high pH to avoid the formation of volatile forms of iodine by processes identical to those that occur in reactor containment smnps. 

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