[en] After the formation by decay of ²²²Rn, the freshly generated ²¹⁸Po ions in recoil routes are most positively charged and react fast with trace gases and vapors in air and become small particles called clusters or, unattached 'decay products', the unattached ²¹⁸Po clusters can react with other aerosol particles and become attached ²¹⁸Po. This process has been accepted in past records. But how the neutralization of the charge ²¹⁸Po happened and the conditions have many uncertainties. This neutralization process is a foundation of radon measurements that depend on electrostatic collection of charged decay products and the dose of radon decay products. This study has been concerned by many scholars in recent years and has obtained many new progresses. Three neutralization mechanisms of ²¹⁸Po were individually described, including electron scavenging by OH radicals formed by radiolysis of water vapor, recombination with small air ions and charge transfer by molecules of lower ionization potential. The three neutralization mechanisms happened differently in different conditions, such as gas concentration in the air, the ionization rate, temperature, the humidity concentration, radon concentration and the age of radon progeny and so on. (authors)

[en] Radon monitor based on electrostatic collection demand for a high and stable collecting efficiency, temperature and humidity influences it greatly. How to get rid of the influence of temperature and humidity is an important problem puzzled instrument developers. The paper discussed the influence of temperature and humidity on the collecting efficiency through experiment. The results show that collection efficiency is related to both relative humidity and absolute humidity, not a function of one of them. The formation and diversification of clusters and neutralization mechanism apply to explain the experimental results. (authors)

[en] The absolute humidity and temperature's effects on the NRL-1 measuring apparatus for radon were studied in this paper. By controlling the radon activity concentration of the radon laboratory in University of South China and improving the temperature and humidity adjust strategy, different correction factor values under different absolute humidities were obtained. Moreover, a correction curve between 1.90 and 14.91 g/m"3 was also attained. The results show that in the case of absolute humidity, when it is less than 2.4 g/m"3, collection efficiency of the NRL-1 measuring apparatus for radon tends to be constant, and the correction factor of the absolute humidity closes to 1. However, the correction factor increases nonlinearly along with the absolute humidity. (authors)