Closed Building Conditions
Stabilizing the rate of radon entry into the building and the indoor air environment through Closed Building Conditions [CBC] is crucial. Measuring radon levels under CBC is crucial for achieving necessary equilibriums for various measurement calculations such as Dynamic and Secular Equilibrium.
Dynamic Equilibrium is the time needed for radon and RDP levels to stabilize once the radon entry rate into a building has been altered (i.e. closed up). 12 hours is normally sufficient for achieve dynamic equilibrium.
Radon is at secular equilibrium with its decay products when the radioactive activity of radon and its decay products are the same. Secular Equilibrium is when short-lived RDPs reach the same concentration in pCi/L as the radon forming them.
Compare and Contrast
|When short-lived RDPs reach the same concentration (pCi/l) as the radon forming them
|Time needed for radon and RDP levels to stabilize once the radon entry rate into a building has been altered
|It takes 4 hours to reach Secular Equilibrium
|12 hours is normally sufficient for dynamic equilibrium to occur in a home
|Justifies the need for closed-building conditions