Abstract: In systems or units for collecting volatile liquids, e.g. refrigerants from scrapped refrigeration systems, the liquid may be successively filled into a closed collector tank, inasfar as the vapor of the liquid as collected in the upper space of the tank will be condensed into the liquid as this rises in the tank. However, there will be separated also an amount of non-condensible gas, e.g. atmospheric air, that will cause a steadily increasing pressure in the tank, so that it is necessary to regularly effect a venting of the tank, that is a gas blow-off, by suitably controlling an upper blow-off valve on the tank.