Why Not Use Mean Kinetic Temperature in Cold Applications? Here’s why…

Back for more on Mean Kinetic Temperature with a customer question:

Hi Paul,
I have reviewed Vaisala’s application note on mean kinetic temperature. But, I am still wondering what particular guidance states that mean kinetic temperature should only be used for room temperature environments and not for refrigerators or freezers? That is Rule #5 on your 6 rules for MKT.
But I’m still unclear to me exactly why not to use it in colder temperatures. Your assistance is greatly appreciated. 

Thank you!
K

Paul Daniel wrote:

Dear K,
Thank you for checking out our training materials! We are happy to provide these to our customers and contacts in the industry at large. Here are the links to the webinar and the application note.

First off, you are not alone in your question, so below I have listed several questions we received in our last webinar on mean kinetic temperature. You will see that your question about cold chambers was asked then as well. And it is a very common question.
Second, to review our application note and the rules you mention, I will list all of them again here.

6 Mean Kinetic Temperature Usage Recommendations:

1. Mean kinetic temperature should not be used to compensate for temperature excursions in any application.
2. When using MKT, ensure you have an adequate number of samples (time/temperature). The more samples that are included in the equation, the more the calculation will represent the actual MKT value.
3. Mean kinetic temperature should not be used in areas where temperature is not well controlled.
4. Use mean kinetic temperature only if the storage temperature specified on the label of the product does not exceed 25˚C.
5. Mean kinetic temperature should not be used for products that require controlled low temperature.
6. Regardless of whether you use the mean kinetic temperature calculation or not, all temperature excursions should be investigated.

Finally, the answer to your question: Why Not Use MKT in Cold Chambers?

Because the best guidance we can use, and probably the only one to use in regulated environments, is the source of the idea that we can use mean kinetic temperature to evaluate temperature excursions: John Taylor.

Here is the name of the paper: The Pharmaceutical Journal (Vol 267), July 2001, J. Taylor. “Recommendations on the Control and Monitoring of Storage and Transportation Temperatures of Medicinal Products.” 

I draw your attention to the lower left-hand corner of page 131 in the paper:

Strict conditions should be applied to the use of mean kinetic temperature. It is applicable only to storage of products under controlled room temperature conditions (I.E., those labeled “do not store above 25°C”). Mean kinetic temperature can be applied to the shipping of these products and it may provide a degree of assurance during prolonged transit periods. Mean kinetic temperature is not appropriate for products requiring controlled low temperature storage and shipping.

This paper basically brought the mean kinetic temperature calculation into its current use and describes how and why to use it. Simply put, the guy who first thought that MKT might be good for evaluating excursions also explicitly stated where not to use it, saying: “[MKT] is not appropriate for products requiring controlled low temperature storage and shipping.” It was a great innovation in its time, but we recommend sticking to the original guidance that accompanied the use of mean kinetic temperature.

That’s why we made recommendation 5 in our application note. We can also find that rates of change in chemical reactions and degradation pathways further support this position.  Our caution against using the value for cold chamber applications is directly from  the seminal paper on the topic, but also from the likelihood that you might have an uphill battle convincing an auditor that mean kinetic temperature for refrigerated chambers is a better solution for evaluating excursions than the other tools we at our disposal. Please contact me further if you have any questions!

Paul Daniel

Leave your comments below and scroll down to see the Q&A from our mean kinetic temperature...