Lab Sensor Solutions | How to Validate That Your Cooler Keeps Things At The Right Temperature
temperature tracking, regulatory compliance
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How to Validate That Your Cooler Keeps Things At The Right Temperature

Maintaining proper environments to preserve medical samples has been a topic of regulatory concern for a long time. In this post, we will focus on medical materials while in transit. In particular, the temperature control of laboratory samples (e.g. blood and urine samples), while they are being transported.

This has been a long neglected area that many labs have recently began to focus on and the advantages are many to monitoring. Once monitoring the actual temperature of totes while in transit, most labs find that they are not well maintained. While for short routes this may not effect the samples, it certainly can and does for longer routes.

Also, many labs have found that the basic process of cooling samples prior to transport is not being followed at the pick up locations. In this case proper temperature is very difficult to achieve during transit. It is important that samples be at the proper temperature prior to pickup.

Because temperature in transit is rarely tracked, this can be a major source of sample integrity errors and can lead to diagnostic errors. It’s widely known that stationary refrigeration systems are closely monitored and maintained. It is just as important to maintain proper temperature while in transit.

Materials You Will Need


Below is a list of materials to collect before starting your validation efforts:

  • A tote used for carrying samples
  • Gel Packs
  • Dry ice (pellets are easier to use)
  • A towel or pad (fits in cooler to separate coolant from samples)
  • Temperature monitor (A wireless one is preferred)
  • Freezer to hold Gel Packs.
  • Spreadsheet or Notebook


Once you have collected all your materials and put them at the proper temperature, it’s time to set up your data collection and monitoring.

Data Collection & Monitoring Setup


We have done several validation studies with a wide variety of coolers. What we have learned is that it pays to make sure that you have everything set up ahead of time before you start. More importantly, it’s vital that your setup be easy to record observations and organized so that when it comes to doing the final report, you don’t have to scramble around to find the data.

The simple process below is a high level outline of how we validate a cooler. It’s just an overview of the detailed process that can take days or weeks to execute. Since we have our own real time temperature monitoring system, the collection piece is automatic but you could use data loggers or a manual thermometer if real time wireless ones are not available.

Step 1: Baseline Your Cooler


Properly place the temperature sensor in your cooler or tote above the ice in the air gap. Sensor placement is critical since you want to measure where the materials will be and not the temperature of the coolant.

Measure and record the temperature of the empty container with your standard coolant present (e.g. 1″ of Dry Ice or 5 Gel Packs). Note how long it takes for the cooler to reach proper the temperature. Also note the ambient temperature of the room. You’ll need this later.

Step 2: Change One Variable at a Time


Start by experimenting with bringing the initial temperature into range more quickly. This is done by letting the cooler come back to room temperature and add more coolant.

For example with refrigerated temperature coolers (2 to 8 C) try placing enough dry ice pellets to cover the bottom of the cooler and leave them in the closed cooler for 10 minutes and then remove them. Note the temperature change and how quickly the cooler comes to proper temperature. This conditioning will allow you to do experiments a lot quicker.

After removing the dry ice pellets, cover the bottom of the cooler with with gel packs. Close it and note how long it stays within temperature range. It’s also a good idea to take intermediate readings, say once every 10 minutes, to be able to look at the trends. Record that in your spreadsheet or notebook.

Step 3: Repeat Step 2 To Dial In Desired Duration


To increase the duration that the tote stays within range, try a few more experiments. Try putting a small amount of dry ice pellets in the bottom of the cooler, cover these with gel packs and then place a towel or other thick cloth over the gel packs. The towel/cloth will eventually be used to protect the samples from direct contact.

Close the lid and monitor how long the temperature is maintained properly. By varying the amount of dry ice and gel packs, you will be able to adjust the length of time a cooler stays within temperature range at a given ambient temperature. Note these configurations in your notebook.

Step 4: Add Sample Analog


Now that you have a baseline for an empty cooler, it’s now time to add a sample analog. This step is done so as not to compromise any perishable materials.

It’s best to use material that simulate your material. For blood tubes, we filled them with saline and put them in the packing material they would normally go into. Repeat the tests above with the desired coolant configuration and record the duration at the proper temperature. You may need to adjust the amount of coolant added but the adjustment should not be that great since you are now adding materials that will also be at the desired temperature.

Step 5: Field Testing


Once you have your setup dialed in, it’s time to put the tote into a real world test by carrying real samples. Do this with a real courier route or simulate the real route in your own vehicle. It’s important to also monitor the temperature as this route is being done so you can see how opening and closing the cooler influences the temperature profile.

As a part of this process, you may realize that the courier may need to add coolant to the tote during a route. This is normal and will most likely be ambient temperature dependent as well.

Also, be aware that you might see a large increase in the temperature of the tote when a large number of samples have been added. This may indicate that the samples were not cooled prior to transport. That’s also good to note in your notebook.

Final Validation Report


As a part of this process, you will want to notate all of the testing you have done and then create a final report that details the process required to keep the tote at the proper temperature. As a part of this you will want to outline the procedures for couriers to follow when coolers are going out of range. Typically, this is required as part of any College of American Pathology (CAP), Joint Commission, or 21 CFR Part 11 checklist and compliance audit.

Real Time Monitoring Does This Automatically


This validation process is much easier if you use some kind of real time temperature monitoring system. That way, you don’t have to constantly be recording temperature in a spreadsheet or log book. It’s also a lot easier to ensure compliance and couriers tend to rapidly learn what works and what does not if they have a real time feedback mechanism.