Measurements of radon daughters in 12,000 Swedish homes.

Lists three factors causing a high radon and radon daughter concentration in Swedish dwellings:< 1. By energy-saving measures the ventilation rate has become low.< 2. 10% of existing houses are built of light-weight concrete with a high proportion of radium.< 3. Large regions have high radium content in the ground.< Describes a method for detecting high radon daughter levels by measuring gamma radiation from the outside. An alternative method is to use filter sampling and a modified Kusnetz method, and at the same time determine the ventilation rate in the dwelling using a tracer gas technique.< States that 15% of the houses investigated have a radon daughter concentration higher then 400 Bq/m*3.