ABSTRACT
The World Health Organization (WHO) recommended the reduction of radon in indoor air to below 100 Bq/m3 (annual average) or, if not possible, proposed to adopt the limit of 300 Bq/m3 and act to phase reduce this exposure (WHO, 2009), as a first step. In addition, the EU recently approved in the Directive 2013/59/Euratom, a reference value of 300 Bq/m3 (annual average) for indoor air (Silva et al., 2014; Silva & Dinis, 2015).
