Q: My fridge door is kept shut by a magnetic strip in a flexible plastic seal. If I attempt to open the door soon after closing it, it seems to be held shut by a vacuum for a few seconds. why is this?
A: Fridge doors stick in this way because opening the door allows some of the cold air to flow out of the bottom of the fridge. If you stand in bare feet at the door of an open fridge you will feel this cold, dense air. This allows warmer air at room temperature into the top of the fridge.
When the fridge is closed again, this new air cools and contracts, creating a partial vacuum and making the door seem to stick. The effect is most noticeable with a freezer compartment, because the lower temperature of the freezer creates an even greater partial vacuum than a fridge does when air at room temperature is introduced as the air undergoes even more contraction.
Advertisement
I have often wondered if the freezing of the water vapour contained in this introduced air adds to the effect inside the freezer compartment. Notice how ice gradually builds up in the compartment of non-defrosting freezers.
To open the freezer door when the temperature contrast between room temperature and freezer temperature is large (on, say a particularly hot day), it is sometimes necessary to prize open the plastic seal a little to allow some air in to equalise the partial vacuum in the freezer compartment.
The partial vacuum created by opening the door soon passes, however, because the door seals are not airtight and the air pressures inside and outside the fridge are equalised by outside air leaking into the fridge compartments.
This means that if you had no idea what the original question was referring to, you should check the quality of the seals on your fridge door 鈥� they may be leaking a lot of cold air and consequently making the fridge work harder than it should have to.