ISO 13164-1:2013 gives general guidelines for sampling, packaging, and transporting of all kinds of water samples, for the measurement of the activity concentration of radon-222. The test methods fall into two categories: a) direct measurement of the water sample without any transfer of phase (see ISO 13164‑2); b) indirect measurement involving the transfer of the radon-222 from the aqueous phase to another phase (see ISO 13164‑3). The test methods can be applied either in the laboratory or on site. The laboratory is responsible for ensuring the suitability of the test method for the water samples tested.