Assertion: gamma ray's source | /r/HasProperty | radon gas
Facets:
Source sentences:
text: An important source of natural radiation is radon gas, which seeps continuously from bedrock but can, because of its high density, accumulate in poorly ventilated houses.
text: An important source of natural radiation is radon gas, which seeps continuously from bedrock but can, because of its high density, accumulate in poorly ventilated houses.