As from 1.1.2018, the limit value of 1000 becquerels per cubic meter (Bq/m3) is replaced by a reference level of 300 Bq/m3 for the average annual concentration of radon gas in "premises where people stay regularly for several hours a day". In addition to this reference level, a threshold value of 1000 Bq/m3 is applicable for the average annual concentration of radon gas at workplaces exposed to radon. Further information can be found in the following note:
Information leaflet (PDF, 164 kB, 21.11.2017) (in French)