Medical refrigerators, also known as ‘laboratory’ or ‘pharmacy’ refrigerators cost a lot more than a standard domestic refrigerator. But how different are they and is the extra money really worth it?
The short answer is, yes, they are worth the extra cost, as they are very different to what you would be able to purchase from an electrical retailer. In this month’s blog, we will examine this in more detail and explain why it is generally not acceptable to use a domestic refrigerator for storing samples or medicines in your laboratory.
There are three key elements to the overall temperature performance of a refrigerator. These are as follows:
Let’s take a closer look at each of these elements and see how they differ between a medical and domestic refrigerator.
All refrigerators will intermittently use a compressor to regulate temperature inside the chamber. The compressor pumps cool air inside the chamber and then cuts out once the desired temperature is achieved. When the temperature begins to rise again, the compressor kicks back into life. The graph below shows how a 4°C temperature medical refrigerator stabilises over a 15 minute period from when the door is first opened:
When the door is closed, the compressor begins to try and get back to the original temperature set by the user. You can see from the graph that the temperature spikes, each time the compressor springs into life. What we find with a domestic refrigerator is that these spikes are much more dramatic which can have an effect on temperature sensitive items.
Notice how the temperature eventually stabilises after 10 minutes with little peaks and troughs. Again, this is the compressor working to try and maintain the 4°C temperature. No refrigerator will be able to maintain exactly 4°C, but what you find is medical refrigerators will better closely maintain this temperature than a domestic refrigerator and the peaks/troughs will be less extreme.
Domestic refrigerators are designed to store food and beverages for personal consumption. Therefore, there is no need for the refrigerator to be specially calibrated, say to UKAS standards. The Food Standards Agency simply advise that ‘the coldest part of the fridge should be below 5°C’.
Temperature accuracy on a domestic refrigerator is generally poor. In fact, many domestic refrigerators do not even have a display telling you what the actual temperature is inside. Therefore, the only way to know what the temperature is doing is by feeding a flexible thermometer through the door seal to take a reading. If you are using a domestic refrigerator in a laboratory environment, it will be impossible to calibrate the instrument without a temperature display.
One of the key issues with a domestic refrigerator is that the temperature is not very uniform. This is because the distribution of air is poor. Air distribution in a medical fridge will be uniform as the shelves are often perforated for better air circulation. In addition to this, there are usually extra fans which move the air around inside the chamber.
It is not unusual for a domestic refrigerator to have a difference of 2°C to 4°C between the top shelf and the bottom of the chamber. Of course, this is perfectly acceptable when storing food or beverages. However, this is not acceptable when storing medicines or patient samples.
If medicines are stored at the incorrect temperature, this poses a considerable risk to patients receiving potentially damaged or ineffective medicines. This would then lead to the user having to discard an entire supply of stock. A recent study in Germany estimated that the average value of medicines being stored in a pharmacy fridge is around €20,000 or around £17,500. Therefore, the cost of losing potentially thousands of pounds of valuable stock is not something the user should take lightly.
There are a number of other features that you will find on a medical refrigerator that you typically won’t find on a domestic one. These feature include:
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