Ventilation rates by direct measurement of radon time-dependent behavior

If a high level is measured in surveying a facility for radon, in lieu of generally expensive physical modifications, the first remedial action to consider should be improvement of local ventilation (air change rate (ACHR)). It would be convenient to be able to determine the ACHR along with the local radon level at the same time that a high radon level is first discovered. Radon level in a space is known to depend on both the source magnitude S and ACHR. This research effort examines the potential of monitoring transient radon levels to establish the ACHR and the radon level at the same time with a single radon detection instrument. Time-dependent equations are developed, with the initial condition that the initial radon concentration is zero at time t = 0 (by purging the space), for 222Rn gas, airborne 222Rn particulate progenies, and 222Rn progenies trapped on a filter detector. If there is no ventilation present, the equations show that the 222Rn gas will seep back into the space and approach the same initial equilibrium level that existed before purging and will reach one-half of equilibrium level in 93.6 h (half-life of 222Rn). If there is ventilation, the buildup rate will be faster but to a lower final equilibrium magnitude than would be true without any ventilation