  The radioactive daughters isotope of 222Rn are one of the highest risk
contaminants in liquid xenon detectors aiming for a small signal rate. The
noble gas is permanently emanated from the detector surfaces and mixed with the
xenon target. Because of its long half-life 222Rn is homogeneously distributed
in the target and its subsequent decays can mimic signal events. Since no
shielding is possible this background source can be the dominant one in future
large scale experiments. This article provides an overview of strategies used
to mitigate this source of background by means of material selection and
on-line radon removal techniques.
