Prediction of radon removal efficiency for a flow-through activated charcoal system and radon mitigation characteristics

Activated charcoal was widely used in radon researches and mitigation applications because of good adsorption ability. In the paper, a simple model that can predict radon removal efficiency (eta) for radon mitigation applications using flow-through activated charcoal system was developed based on the previous works. Experiments were conducted with a flow-through activated charcoal system to validate the model and study the influence of factors on eta. The experimental results of eta are consistent with the theory to within 4% at the flow rates of 1-3 L/min, but range from 2% to 14% at the flow rates of 4-5 L/min. The equilibrium time of radon linearly decreases with rising flow rate, and eta decreases with rising flow rate. With moisture competing with radon for adsorption sites on the activated charcoal, radon reaches the equilibrium concentration more quickly than moisture does. As relative humidity increases, eta decreases, but the radon equilibrium concentration increases. The values of eta are bigger for those smaller particle sizes with the same type of activated charcoal. The results of this paper are useful for designing activated charcoal systems at indoor environmental conditions and predicting eta for radon mitigation applications.