Characterisation of the Aerosol and the Activity Size Distribution of Radon Daughters in Indoor Air

The aerosol size distribution in 11 dwellings was measured using an electrical mobility analyser (TSI 3030). Large variations in the aerosol concentration, e.g. in connection with cooking and smoking were detected both within a single dwelling and between different dwellings. A typical size distribution shows an area median diameter of 0.2 µm with a geometrical standard deviation of about 2. Variations in the particle size distribution were observed, e.g. cooking decreases the median size of the particles whilst smoking increases the size. Through a modification of the TSI 3030 the activity of the radon daughters distributed on different particle sizes can be assessed. Measurements were performed both in the laboratory and in a dwelling showing an activity distribution close to the particle area distribution. Large variations in the unattached fraction of radon daughters due to variations in the aerosol concentration of the dwelling were observed