Effective Removal of Airborne 222Rn Decay Products Inside Buildings

Abstract

Comparisons were made of the effectiveness of various indoor air treatment methods in reducing the lung dose due to inhalation of 222Rn decay products. The comparisons were based upon measurements of the total steady-state concentrations of 218Po, 214Pb and 214Bi, and the concentrations of these nuclides not attached to particles. These measurements, which were made inside a 78-m3 room before and after air treatment, were used along with a state-of-the art lung dose model to predict reductions in the dose to the radiosensitive bronchial tissues. Results suggest that flow-through air-cleaning methods, such as filtration and electrostatic precipitation, although effective in reducing total potential alpha energy concentration, cause a greater quantity of airborne potential alpha energy to be unattached to particles. This may result in a substantial increase in the dose to bronchial tissues. The optimal form of air treatment appears to be a combination of nonuniform positive space charge generated by an ion generator and enhanced convection from a fan. This combination of air treatment gave reductions in the mean dose to the bronchial tissues of up to 87%.

Impact from indoor air mixing on the thoron progeny concentration and attachment fraction

“…On the contrary the unattached fraction obtained with the CFD model demonstrates a reduction by approximately 50%. These computational results are consistent with earlier studies that demonstrate a decrease in unattached fraction when ventilation or air recirculation is introduced (Maher et al, 1987), whilst maintaining a constant aerosol concentration. The experimental study by Maher et al (1987) demonstrated a 50% reduction in EEC Rn and 60% reduction in the unattached fraction (f Rn ) for a similar case with indoor mixing fan switched on.…”

“…The largest reductions were mostly achieved with regular commercial air cleaning devices; however, also the use of enhanced air mixing resulted in a significant reduction. Similar effects have also been reported by others (Rudnick et al, 1983;Bigu, 1983;Maher et al, 1987;Kozak et al, 2014), who observed a significant decrease in radon progeny of around 40% when air-mixing fans were used.…”

“…Previous work carried out by Van Dijk (1995, 2002) and Maher et al (1987) has focussed on the efficacy of such mitigation strategies as listed under stage four. The work was specific to 222 Rn, but demonstrated considerable reduction in progeny concentrations when using enhanced recirculation and air cleaning devices based on ionising of the air.…”

Indoor Radon and Its Decay Products: Concentrations, Causes, and Control Strategies

“…1987). Recent experimental work by Maher et al (1987) suggests that combining the use of an ion generator with a mixing fan is an effective method of air cleaning for reducing radiological dose from radon decay products.…”

Efficiency of a Portable Indoor Air Cleaner in Removing Pollens and Fungal Spores

“…These systems include portable filters, ionizers, and electrostatic precipitators (ESPs). Air cleaners have been evaluated extensively for removal of radon progeny (Hinds et al, 1983;Li and Hopke, 1991;Maher et al, 1987;Rajala et al, 1987) and have been found to be more effective than electronic systems. Offermann et al (1985) evaluated 11 different types of portable air cleaners including panel filters, ESPs, and ionizers for removing tobacco smoke in a well-controlled room.…”