When a vacuum pump purges non-condensable gases (such as hydrogen) from the LiBr absorption unit, it inevitably draws in small amounts of lithium bromide solution vapor and refrigerant water vapor.

These vapors condense into liquid (primarily a mixture of water and trace lithium bromide) upon encountering the cold surface within the oil trap.

Simultaneously, vacuum pump oil mist carried in the vacuum pump exhaust may also condense within the oil trap. The valve is designed at the lowest point of the oil trap, serves to periodically or as needed safely discharge this condensed oil-water mixture (i.e., “contaminants”) into a dedicated container, preventing its accumulation within the oil trap.