lucy, from working in housing for many years and condensation being a big problem , humidity of 80% and above will condense on a surface below 20 degrees , dont know if this info is accurate or of any use to your problem

LucyD, I am guessing low voltage testing?

Lucy, I am kind of guessing you mean 43kV not kW? Just to add insult to injury, it's a lower case letter k, & kW is not a current it's a power! ;) ;) ;) So, if you are at HV which 43kV is, then yes humidity will definitely affect the readings, as you will get all sorts of effects. Which part of 60060 are you referring to? -1, -2 or -3? I was kind of guessing -3 as you are testing on site, but it seems you are looking at -1. Looking at the para you quote, it does detail the 80% value. Yes it does relate this to test quality, and that is valid. I would also be wary of the chances of chaotic tracking over the test equipment, so I would go with the people who are doing the testing. Also once the humidity gets to a critical level, then any contamination on the EuT or the test equipment can have an effect on the tracking, so both on the results and the safety.