When the mapping study says move the probe, do you need other criteria to relocate?

In this week's blog, Senior Regulatory Expert Paul Daniel offers some practical advice on moving probes in validation/mapping. Plus, you are invited to a webinar on sensing vaporized H2O2 in biodecontamination.

We received two questions by email...

Question 1: How do you recommend we assess the worst case in different environments (both hot and cold environments)?

Question 2: For periodic remapping, what are good acceptance criteria for changing a monitoring probe’s location?

Your Best Shot at creating a Worst Case Plus... Temperature Probe Relocation Know-how

Paul writes:
In temperature mapping, worst case depends on the use.  For a refrigerator, it could be the hottest or the coldest point (or both).  If the refrigerator is used for storing vaccines, cold is worse than hot.  For an oven, it depends on your criteria.  If you are depyrogenating, the worst case would be the cold spot. But your material might have an upper specification as well.  In the end, we recommend that you look for both the hottest and coldest spots in any environment… the extremes tell the story. One exception is freezers, where it is usually only the hottest spot that is important.

For your second question, I admit that it that only comes up occasionally and from those with some long-term experience in mapping.  The easy answer is that you should simply move the monitoring probe to the hot spot/cold spot.  But this gets complicated in two ways: first, most people don’t actually monitor the hot spot/ cold spot … they monitor an area on the wall that is representative of the hot spot/cold spot.  Second, if you find a different hot or cold spot during your remapping, it implies something has changed in the system.  

Simply provide the data that shows that there is a better place for the new probe location.

At this point you may need to go back to your historical mapping data to show that it is not unusual for this unit to have a new hot spot – likely the new hot spot would have been the second hottest spot in the old mapping study.  I wouldn’t worry about it too much unless your QA department gives you a lot of push-back.  Simply provide the data that shows that there is a better place for the new probe location. And be prepared for QA to ask for your help to show that no problems might have gone unnoticed by having the probe in the wrong location.

Thanks for reaching out and please let us know if you have further questions!
Paul Daniel

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