The hygrometer guides the monitoring of the humidor. Checking it against a known reference makes it possible to know whether the instrument’s reading matches that reference’s value.

Boveda explains a test with its calibration kit at 75 % relative humidity. It indicates placing the instrument in the kit’s sealed environment for at least 24 hours and maintaining the conditions the manufacturer specifies. The reading obtained is then compared with the reference value.

If the instrument allows adjustment, it should be carried out according to its manual. Otherwise, the difference can be noted in order to interpret the readings. The suggested record is to keep the date of the check, the reference used and the deviation observed. Repeating a check requires following the instructions of the sensor’s manufacturer and of the kit. The result documents the instrument’s behaviour in that test; keeping the history makes it possible to know against which reference the collection’s data are being read.