Effect of pressure drops on radon exhalation from walls

The exhalation of radon (222Rn) from walls was measured in a concrete-walled basement room by studying the growth of activity in exhalation cans sealed to various portions of the walls. In a series of measurements, constant underpressures from 5 to 25 mm Hg were maintained in the exhalation cans during the build-up of activity. The exhalation rate appears to increase linearly with the underpressure. In the theoretical considerations of pressure drops, it is assumed that the basement concrete walls in toto are capable of sustaining for many hours underpressure-enhanced exhalation values comparable to those experimentally measured at various places on the walls. The fractional increase in room air activity is proportional to the total pressure drop and increases with the time it takes the pressure drop to establish