Medical refrigerators, also known as ‘laboratory’ or ‘pharmacy’ refrigerators, are significantly more expensive than regular household refrigerators. But how different are they from domestic and underbench freezers? and is it really worth the extra cash?
The quick answer is that they are well worth the extra expense because they are unlike anything available from a domestic appliances retailer. In this blog, we’ll go over this in further depth and explain why using a domestic refrigerator to store samples or medicines in your laboratory is generally not a good idea.
Temperature performance
The entire temperature performance of a refrigerator comprises three major factors. The following are the factors:
- Stability- How well does the refrigerator keep the temperature it’s set at?
- How accurate are the readings on the refrigerator in comparison to a calibrated standard?
- Temperature uniformity—How consistent is the temperature inside the chamber?
Let’s look at each of these components in more detail to understand how they differ between a medical and a residential refrigerator.
Temperature stability
A compressor will be used sporadically in all refrigerators to adjust the temperature inside the chamber. Once the desired temperature is reached, the compressor stops pumping cool air into the chamber. The compressor comes back on when the temperature starts to increase again. The graph below depicts how a 4°C temperature medical refrigerator stabilises after the door is initially opened over a 15-minute period:
When the door is shut, the compressor tries to restore the temperature to the user’s original setting. The temperature spikes each time the compressor kicks on, as you can see from the graph. When we use a household refrigerator, we notice that the temperature spikes are much more dramatic, which can affect temperature-sensitive objects.
Observe how, after 10 minutes, the temperature gradually stabilises with little peaks and troughs. This is the compressor at work again, attempting to keep the temperature at 4°C. Although no refrigerator can maintain a constant temperature of 4°C, medical refrigerators tend to do so more precisely than home refrigerators, with less dramatic peaks and troughs.
Temperature accuracy
Refrigerators for home use are designed to keep food and beverages for individual usage. As a result, the refrigerator does not require extra calibration, such as to UKAS standards. ‘The coldest portion of the fridge should be below 5°C,’ says the Food Standards Agency.
A household refrigerator’s temperature precision is typically low. Many residential refrigerators, in fact, lack a display that indicates the actual temperature inside. As a result, the only way to determine the temperature is to insert a flexible thermometer into the door seal and take a reading. It will be impossible to calibrate an instrument without a temperature display if you use a domestic refrigerator in a laboratory equipments.
Temperature uniformity
One of the major drawbacks of a residential refrigerator is that the temperature is not consistently maintained. This is due to insufficient air dispersion. Because the shelves are generally perforated for greater air circulation, air distribution in a medical fridge will be uniform. In addition, there are frequently additional fans that circulate the air within the chamber.
A variation of 2°C to 4°C between the top shelf and the bottom of the chamber is not uncommon in a residential refrigerator. Of course, when storing food or beverages, this is totally permissible. When storing drugs or patient samples, however, this is not permissible.
