Abstract
The calibration curves for standard EPA open face and diffused barrier charcoal collectors were extended for moving air environment applications. The response of charcoal to variable radon concentration at different temperature and humidity was studied using a radon chamber. The average radon concentrations were measured in two different districts of different soil natures in Cairo, using simultaneously activated charcoal and AB-5 active monitor. The measurements show that the average radon concentration in houses constructed on limestone nature soil is higher than in those constructed on clay nature soil. The active monitor data showed that radon concentration increases during nighttime and decreases during day.