Five Reasons to Increase Temperature Monitoring Probes: increasing space, product price or sensitivity, temperature differential, & cooling system reliability

Paul Daniel, Vaisala
Senior GxP Regulatory Compliance Expert
Industrial Manufacturing and Processes
Life Science

In this week's blog, our Senior Regulatory Expert give five situations where you will want to consider increasing the number of probes. Plus - we invite you to a webinar on mean kinetic temperature.

Dear Paul,

Thanks for the help you have given us in the past… I have a couple questions for clarification regarding monitoring for temperature excursions. Ideally how many monitoring probes would you recommend for daily monitoring? Is the number of monitoring probes dependent on the area?  

Second, do you recommend placing the sensors at the warmest, or coldest spot? For instance: we have just one monitoring probe in a large walk-in, either 2-8°C or -20°C. This has been our biggest challenge… 

Truly appreciate your help! 

Best regards, 


Paul´s reply

Hi S, 

Yes, you would expect to see more monitoring probes in a controlled space as the size of the space increases.  

You also expect to see more monitoring probes as…

  1. The temperature sensitivity of the product increases.
  2. The price of the product increases.
  3. The temperature differential between the inside/outside of the area increases.
  4. The reliability of the cooling system decreases.

In the end, it is a risk-based decision.  There is no solid rule. However, more warning letters and observations are seen for not monitoring at all, than for not having a high enough density of monitoring probes.  

Pick a density of probes that makes you feel safe and confident.  I have seen people examine their mapping studies, decide a distance (generally arbitrarily) to say no product should be more than X meters from a probe, and then come up with a probe layout based on that logic.   For instance, I know one distributor who wants all products (in ambient storage conditions) to be within 25 meters of a monitoring probe. 

But for anything under 20 cubic meters, you are generally fine with one probe.  It does not need to be at the warmest / coldest spots.  But it should be placed at a spot that does take that data into account.  Most hot spots/cold spots are inconvenient, expensive, or dangerous to monitor.  Find a place nearby that is representative.  In the end, almost every manufacturer puts the sensor near the door, out of the way of traffic, in good airflow, and out of the way of spaces that can be used for storage. 

Best Regards,


Mean Kinetic Temperature Webinar

Vaisala's Senior Regulatory Expert Paul Daniel provides you with 6 clear Do's and Don'ts for using the calculation, including where it is useful in decision-making for regulated industries, and where it is not.

You will leave the webinar with an understanding of MKT as a non-linear weighted average that shows the effects of temperature variations over time. Included is a Q&A section where live webinar participants asked about best practices for MKT in their own controlled environments. 

Key Learning Objectives

  1. References and resources for MKT calculation
  2. The Arrhenius equation and the non-linear effect of temperature excursions
  3. How regulatory bodies (like the FDA and EC) recommend MKT
  4. What data to use when MKT is not appropriate



Paul Daniel, Vaisala

Senior GxP Regulatory Compliance Expert

Paul Daniel has worked in the GMP-regulated industries for over 25 years helping manufacturers apply good manufacturing practices in a wide range of qualification projects.  His specialties include mapping, monitoring, and computerized systems.  At Vaisala, Paul oversees and guides the validation program for the Vaisala viewLinc environmental monitoring system.  He serves as a customer advocate to ensure the viewLinc environmental monitoring system matches the demanding requirements of life science and regulated applications.  Paul is a graduate of University of California, Berkeley, with a bachelor’s degree in biology.

Janice Bennett-Livingston

Marketing Manager

In addition to editing the Vaisala Life Science blog, Janice Bennett-Livingston is the Global Life Science Marketing Manager for Vaisala's Industrial Measurements business area.

Pre-Vaisala writing credits include a monthly column called "Research Watch" for Canada's award-winning magazine alive, as well as articles in Canadian Living and other periodicals. Other past work: copywriting for DDB Canada, technical writing at Business Objects, and communications specialist for the British Columbia Child & Family Research Institute.

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