The time it takes for a refrigerator or freezer to lose all its coolness when the door is left open slightly can vary depending on several factors, including the make and model of the appliance, the ambient temperature of the surrounding environment, and the initial temperature setting of the appliance.
Generally, a refrigerator or freezer is designed to be well-insulated and maintain its temperature for a certain period even if the door is left open slightly. However, the more the door is open, the faster the cooling will be affected.
If the door is only slightly ajar, the cooling loss will be relatively slow, and the appliance may take several hours to warm up significantly. In most cases, you might notice a difference in temperature within a couple of hours, but it could take up to 4 to 6 hours for the appliance to reach a dangerously warm temperature.
The best practice is to avoid leaving the refrigerator or freezer door open for extended periods to prevent unnecessary energy consumption and potential food spoilage. If you accidentally leave the door open, make sure to close it as soon as possible to maintain the temperature and preserve the freshness of the food inside.