Difference between medical and domestic refrigerators

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.

Temperature performance

There are three key elements to the overall temperature performance of a refrigerator. These are as follows:

• Stability- How well does the refrigerator maintain the set temperature?
• Accuracy- How close do the readings on the refrigerator match a calibrated standard?
• Uniformity- How uniform is the temperature in the chamber? For example, is there a big difference between the top and bottom or are there any ‘hot-spots’ within the chamber?

Let’s take a closer look at each of these elements and see how they differ between a medical and domestic refrigerator.

Temperature stability

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.

Temperature accuracy

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.

Temperature uniformity

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.

Other benefits of a medical refrigerator

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:

• Extra fans- Many medical refrigerators are equipped with extra fans or at least a more heavy duty single fan to cope with hot conditions. Many labs are air conditioned, although they can still be hot places to work with large numbers of people and equipment generating heat.
• More sturdy door construction- the doors of a medical refrigerator may be opened and closed dozens of times a day. This is why the door seals and hinges are more sturdy as they are designed for heavy use.
• Low noise- Laboratories can be extremely noisy places with the sound of people talking combined with centrifuges spinning or robotic units processing samples. Medical refrigerators are often a lot quieter which helps keep the overall noise levels down.
• Visual and/or acoustic alarms- With the increase in noise level means that often users will need a visual and/or audible alarm to alert users when the door is left open.
• Energy consumption- Unlike in a domestic setting, laboratories, pharmacies and hospital departments will have several refrigerators in one room. When we consider the number of refrigerators over the whole site, we could be talking about hundreds of devices. This is why power consumption is so important for fridges used in a medical setting. Domestic fridges are already rated on their energy efficiency but medical refrigerators tend to be even more energy efficient.

How Henderson Biomedical can help with your medical refrigerator needs

Henderson Biomedical is an official UK distributor of Vestfrost refrigerators and freezers. We are also authorised to sell Gram and Labcold products, which are commonplace in a laboratory setting.

For more information on how we can help you, please contact our team on 020 8663 4610 or you can email us at info@henderson-biomedical.co.uk.