In steam generation plants with open-air condensate systems, heat recovery from steam escaping into the atmosphere from the condensate tank (flash steam) occurs as follows: Steam produced in the boiler at a certain operating pressure releases its latent heat at the point of use, condenses at the operating pressure, and passes through the condensate trap as water, reaching the condensate line connected to the atmosphere (open air). Due to the pressure drop, some of the water formed as a result of condensation evaporates again (flash steam), and the water-steam mixture comes from the condensate line to the condensate tank. While the water fills the condensate tank, steam escapes from the vent pipe of the condensate tank and goes to the atmosphere. These leaks increase if the condensate traps are incorrectly selected or faulty.

In many facilities that use steam, a white cloud of steam rising from the side of the boiler room is an indicator of this phenomenon and is perceived as if it were a natural occurrence. If precautions are not taken, 10-15% of the condensate returning to the condensate tank escapes into the air as flash steam leakage.