The steam that you see coming out from the top of a freezer when you open it is not actually steam but rather condensed water vapor. This phenomenon occurs due to the temperature difference between the inside of the freezer and the surrounding air.
When you open the freezer door, warm and humid air from the surrounding environment enters the freezer. The cold temperature inside the freezer causes the moisture in the air to condense into water droplets. This condensation appears as fog or "steam" when it comes into contact with the colder air inside the freezer.
The moisture in the air can come from various sources, such as ambient humidity or moisture released by the food items stored in the freezer. The colder air inside the freezer cannot hold as much moisture as the warmer air outside, leading to the condensation of water vapor.
It's important to note that this condensation is a normal occurrence and does not indicate any issue with the freezer. However, excessive condensation or a consistent buildup of ice could be signs of a problem, such as a faulty door seal or temperature control. In such cases, it may be advisable to have the freezer checked by a professional.