Measuring radon exhalation rate by tracing the radon concentration of ventilation-type accumulation chamber

•We present a method for measurements of radon exhalation from the medium surface in open loop.•The real radon concentration of ventilation-type accumulation chamber can be obtained by correction algorithm.•The radon exhalation rate can be obtained by nonlinear or linear least squares fitting.•This method can be applied for develop the portable instrument.

Radon exhalation rate is crucial in the estimation of radiation risk from various materials. RAD7 only focus on the count of the 218Po in sniff mode, and is well suited to measure radon exhalation rates. This paper presents a fast method for measuring radon exhalation from medium surface with a ventilation-type accumulation chamber by the RAD7 while making the effects of leakage and back diffusion negligible. The radon exhalation rate can be obtained from the measured values before radioactive equilibrium between Radon and progeny occurs. This method is based on the principle for tracing radon concentration changes by deriving 222Rn concentrations through 218Po measurements. Several radon exhalation rate measurements of medium surface have been performed in the Radon Laboratory of the University of South China. The radon exhalation rates obtained by verification experiments are within the accepted values for the reference value.