Examination and sampling: when to sample
You should arrange for a sample for analysis to be taken when instructed to do so by a CHIEF profile.
Some of these profiles are to address a specific identified risk, while others are a Regulatory requirement.
Sampling is undertaken by the UKBA on instructions from the NCH.
It should be made clear to the UKBA precisely why they are sampling and what needs to be established, as they will need to put this information in their instructions when sending the sample off for analysis.