Paul Daniel

Jul 25, 2018
Gerardo –

Thanks for your reply! I will hope you will allow me to disagree a little.

I have never observed a steady state condition in any environment I have ever mapped (other than perhaps a LN2 dewar). It is extremely hard to achieve a steady state environment when trying to perform a calibration. Every environment shows some variability as the control circuit engages to heat or cool the space.

Your basic premise is certainly correct, that is: if the environment (air temperature) is within specification, then the product will be within specification. But the reverse is not true – if the environment (air temperature) is out of specification it does not mean the product is out of specification

As an extreme example, I once mapped a refrigerator storing 1L bags of human blood with specifications of 1C to 10C. The air in the refrigerator varied widely, from -1C up to 13C. The product varied a little ranging from 4C to 5C. This was a clear example of the environment failing, without the product failing.

If I understand you, I think you are recommending to map both air temperature (for equipment qualification) and product temperature (for qualification of the monitoring process). And I agree with you that this is the most circumspect and risk-averse approach. From my own experience and from the questions I receive on how to map from our customers, most companies do not have the resources (time, equipment, expertise) to do both. They want to do the best they can with the resources at their disposal. Therefore, that has led us to recommend that if you can only map one of the conditions, you should map the air temperature, not the product temperature.

Thank you for reading and responding to our blog! We welcome questions and comments exactly as you posted!

Best Regards,

Paul Daniel