Study on the effect of Fresh Air Ventilation system for reducing indoor ^(222)Rn

Objective:To explore the reduction effect for the indoor ^(222)Rn(Rn)by Fresh Air Ventilation(FAV)system,a novel commercial ventilation device in China.Methods:The indoor concentrations of Rn and its decay products(RnD)in three residential rooms,two in Beijing and one in Hefei city,Anhui province,before and after FAVS functioned were measured using an active continuous method.The air exchange rate was monitored by measuring CO_(2) concentration using the tracer gas method.Results:In the three rooms,the FAVS reduced the Rn concentrations from(162±80)Bq/m^(3) to(63±22)Bq/m^(3) and decreased the RnD concentrations from(64±35)Bq/m^(3) to(13±6)Bq/m^(3) on average,a decrease of(59±25)% in the Rn concentrations and a drop of(77±18)%in the RnD concentrations.Considering dose conversion factors of Rn and RnD,FAVS decreased the exposure dose by(76±20)%.Besides,FAVS increased the air exchange rates from 0.17 h^(-1) to 0.56 h^(-1) on average.Conclusions:FAVS can effectively reduce indoor Rn and RnD concentrations by improving the air exchange,serving as a valuable supplement to existing radon mitigation methods,especially in extreme climates.

Analysis and Monitoring of Indoor Radon Concentrations of 37 Kindergartens — Beijing Municipality, China, 2023

Introduction:Radon(222Rn or 222radon)is a radioactive gas emitted from building materials,foundations,and soil.Children are especially susceptible to radon exposure,underscoring the need to assess indoor radon levels in kindergartens.This study monitored radon concentrations in 37 Beijing kindergartens from June to October 2023.Methods:A random sample of 37 kindergartens was selected from 18 administrative districts in Beijing.The indoor radon concentration was measured using the solid track accumulation method,with radon detectors continuously monitored over a 3-month period.Results:The mean indoor radon level in 37 kindergartens,observed at 252 monitoring points,was 84.3 Bq/m3,with values varying from 12.9 to 263.5 Bq/m3.About 20.2%of points showed radon levels between 100.0 and 200.0 Bq/m3,while 2.4%exceeded 200.0 Bq/m3.Notably,radon levels were significantly elevated on the ground floor compared to the upper floors.Conclusion:Indoor radon levels in 37 kindergartens remained below the national standard limit of 300.0 Bq/m3 for buildings(GB/T 16146-2015).Nonetheless,18.9%of the kindergartens exceeded the 100.0 Bq/m3 limit set for new constructions.It is advised to improve radon monitoring in kindergartens and consider developing a national standard for maximum permissible radon levels in such facilities.