An Ultra-Low freezer should be designed to prevent stored materials from being exposed to warmer temperatures. Accessing the contents of an Ultra-Low Temperature Freezer is a regular occurrence that should not have a dramatic impact on the temperature throughout the entire cabinet. However, there are significant differences in how various Ultra-Low freezers are designed and how well they safeguard samples and other stored products during door openings.
One factor that is critical to protecting samples during door openings is the design of the inner doors. Ultra-Low Freezers typically have an inner door for each shelf within the unit, in addition to the heavy-duty outer door. This creates enclosed storage compartments within the freezer. When one of the inner doors is opened, the design should prevent warm air from entering the other compartments.
Since door openings are a routine occurrence, we set out to evaluate what happens to the temperature inside the freezer when both the outer door and one of the inner doors are opened. Two Ultra-Low Freezer models were tested, one from Helmer Scientific and one from another manufacturer. A key difference between the two models is that one has inner doors that are sealed with gaskets, while the other has inner doors that are not sealed. The purpose of the gaskets is to seal the space between the doors to prevent warm air from entering the compartments and affecting the temperature of the samples. The two units were tested to determine the increase in cabinet temperature when the outer door and also one inner door are opened to a 90º angle.
We anticipated that well-designed inner doors, fully sealed with gaskets, would have some impact on freezer performance. We were surprised to learn what a dramatic difference the design of the inner doors makes. Download the white paper to learn how critical this feature is to protecting samples from temperature increases due to door openings.