Where is it a requirement of ISO to record the relative humidity on certificates of calibration? We list the range in our calibration procedure, but can not find where that reference range came from.
If any one can let me know please do so.

If you don't mind, I moved your post over to it's own thread, where you might get better feedback.

Are you performing the calibration on instruments? Or, does this have to do with instruments someone is calibrating for you?

In your procedures, do you have any references to observing/ recording temperature/humidity, or make any statement about an appropriate range?

What instruments are you calibrating here? Are they affected by temperature/humidity?

Where is it a requirement of ISO to record the relative humidity on certificates of calibration? We list the range in our calibration procedure, but can not find where that reference range came from.
If any one can let me know please do so.

Are you referring to the RH of an instrument or the environmental controls for the testing laboratory ?

ISO/IEC 17025 standard does not state that you must take RH readings for any test. It's not that specific.....

You are probably using a procedure that has no traceable origin. Nobody knows where this specific RH range came from. You need to be able to explain "why" you've restricted yourselves to this RH range.

Some standards & procedures are very sensitive to RH. A lab with a very small deviation of RH throughout the day will show more stable readings over time. Environmental stability can be a significant contributor to uncertainties.

Long story, short....... You need to know why you have these RH requirements in your procedures. It's easy to say "Because of ISO", but this is a rather ignorant statement and will be pounced upon by an auditor. They do smell fear, you know?

There are many people here that can provide more help than me...... I think that will require more specific info from you.....

What are you testing/calibrating?

Kbliese,
The ISO 17025 requirement to record environmental conditions on the certificate where relevant is clearly in 5.10.4.1 (a), but if you want to justify not reporting humidity what you are missing is the result of your own test, for example what is the influence factor of 20 % RH versus 80 % RH on your quantity to be measured.