During the ocean transportation or storage of containers, the huge temperature difference between day and night on the sea makes the water-rich high-temperature air locked in the container during the day super-saturated due to the temperature decrease at night. The container will often experience the high temperature and high temperature of the ocean. The temperature difference between day and night changes, the temperature will change between 0 °C and 80 °C, and the humidity will be as high as 98%. This is the condensation phenomenon. When the temperature is 30 ° C, the water content in the air is 30.4 g / m 3 , when the temperature is reduced from 30 ° C to 18 ° C, the water vapor content will drop to 15.4 g / m3. Other water vapors condense into water, which is commonly known as "container rain."