Negative ionisers have been proved to be effective in reducing indoor particulates in general and activity concentrations due to radon and thoron ((220)Rn) decay products in workplace environments in particular. However, in comparison, there exist few studies on the effect of positive ions for mitigation. In the present work, particle and activity concentration reduction has been compared for three experimental conditions (two for positive ions and one for negative) in an unoccupied room with elevated (220)Rn levels. The negative ioniser configuration provided a better concentration reduction factor of 4.59 with smallest characteristic depletion time. A theoretical estimate of the dose reduction factor is found to be 3.96 and 3.74, respectively, for positive and negative ioniser configuration.
http://rpd.oxfordjournals.org/content/early/2011/04/05/rpd.ncr063.full.pdf+html
http://www.ncbi.nlm.nih.gov/pubmed/21471127