The vapors that come out of a freezer are typically water vapors or steam. When you open a freezer door, warm air from the surroundings enters the freezer. This warm air comes into contact with the extremely cold temperatures inside the freezer, causing the moisture in the air to condense and form water droplets or frost on the freezer surfaces.
When you close the freezer door, the air inside the freezer gradually cools down, causing the moisture on the surfaces to freeze. When you open the freezer door again, the sudden influx of warmer air causes the frozen moisture to melt, resulting in the release of water vapors or steam. These vapors are simply the result of the condensation and subsequent evaporation of moisture present in the freezer.
It is worth noting that excessive frost or a constant presence of vapors could indicate a malfunction in the freezer, such as a faulty seal or temperature control. If you notice abnormal or persistent vapor production, it is advisable to consult the manufacturer or a professional appliance repair service to investigate and address any potential issues.