Trusting Fans for Temperature Uniformity Vs. Loading Styles & Mapping Studies

Warehouse cold chain
Paul Daniel, Vaisala
Senior GxP Regulatory Compliance Expert
Published: Nov 28, 2017
Life Science
We received this question from a customer performing mapping studies in fridges and cold rooms:

Dear Paul,

In mapping a cold chamber or room, what do you think about a high-volume recirculating fan for achieving temperature uniformity? We are talking about volume complete air turnover every minute or two. Isn’t it so that this type of fan will reduce stratification and increase thermal uniformity by creating a highly turbulent situation inside the area?  So, my question is...
If we move the air in a fairly constant manner, can we create temperature uniformity from top to bottom of a chamber or room?
Thanks for any advice you can offer!

Dear C,

In our experience most refrigerators and cold-rooms that cool by blowing air don't have too many problems with stratification.  It doesn’t take too much flow to break up any gradients that could affect temperature uniformity. However, what we commonly see are either temporary cold spots in front of the cooler vents, or lingering hot spots in dead spots that aren't receiving air flow. The reasons can differ, but the lack of air flow is usually because they are outside of the flow pattern, either permanently (such as a high corner) or temporarily (behind a blockade of load items). I hesitate to presume that a fan that runs – as you say – every minute or two, is enough to presume de-stratification.
Thermal validation to find Problem Areas
Refrigerator Monitoring
Fans can move the air, mapping study data will show you the effects of that movement.
These problems are solvable, by marking the permanent dead spots as off-limits, and controlling the temporary dead spots with proper loading procedures.  You might find it useful to look at information on refrigerated trucks because they deal with dead spots in the load quite often. Air circulation is managed with loading methods, fans, sensors and understanding the behavior of the storage chamber under different conditions through studies.
Here is a great document on refrigerated vehicles (reefers) from World Health Organization:
While a lot of the info in this document has to do with transport-specific items like labeling procedures, there is a focus on loading methods that ensure air flow for temperature uniformity in a given area.
“Allow for air circulation completely around product, including the bottom.”
Here is another article on reefer trucks in cold chain: “Cold Chain in Logistics” from Hofstra University. It gives an operational overview of refrigerated transport. From Dr. Jean-Paul Rodrigue, Dept. of Global Studies & Geography , Hofstra University, New York, USA


Once you perform your mapping study, you'll know the challenges of your particular design.  Most designs or load patterns have at least some challenges with temperature uniformity. We just need to find out which ones you have. The point is that you can’t use equipment – fans and the like – to take the place of what you need to learn from thermal mapping studies.
Thank you for reaching out! For a bit more detail on balancing the specifics of your environment -- equipment, doors, windows, shelving, loading practices, etc.
Included in this blog, we offer an infographic on data integrity in your monitored environments. This infographic gives a quick summary of the data management practices regarding your environmental monitoring that we find most important in our customers' audits and inspections. See below...
data integrity


Download this infographic for a quick overview of the most important for data integrity in monitoring.



Paul Daniel, Vaisala

Senior GxP Regulatory Compliance Expert

Paul Daniel is the Senior GxP Regulatory Expert at Vaisala. He has worked in the GMP-regulated industries for over 20 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.

Add new comment