The U.K. MHRA have an interesting blog post on GDP and temperature mapping. Here is an excerpt:
"Temperature monitoring equipment should be located according to the results of the mapping exercise, ensuring that monitoring devices are positioned in the areas that experience the extremes of fluctuations.
The mapping exercise should be repeated according to the results of a risk assessment exercise or whenever significant modifications are made to the facility or the temperature controlling equipment."
For more details see MHRA Blog.
Posted by Dr. Tim Sandle