Condensation may occur when the temperatures of a surface is lower than the surrounding media. For example, you see it on the cold surface of a can of coke.
When the media is warmer than the filter condensation may occur in the filter. This can affect and even damage the media flowing through the filter. In many processes, the product can become defective or measurments become inaccurate if the media is exposed to condensation during the process.
To prevent this, a thermal blanket (AQ Heater Jacket) is put on the filter housing, heating the filter to desired temperature. Now when the filter is hot, condensation does not occur.
For more information, download the product datasheet
or the manual: