Volatile toxic gases may with the passage of time, gradually reduced to the level of security, but not because of time indoor radon reduction, and its parent radionuclide half-life is very long.

• 挥发性有害气体可能随着时间的推移，逐渐降低到安全水平，但室内氡不会由于时间的推移而减少，而且它的母体核素半衰期很长。