A system for re-starting an air separation plant after an interruption in operation wherein descending liquid is collected in a non-operating distillation column and passed back to the separation section of that column before or upon re-start. The invention may employ a collection device situated in the column above the sump. Upon interruption in operation, the collection device accumulates descending liquid. From the collection device, liquid may be passed outside of the column and transferred to a holding vessel to re-inventory internal material of the column upon resumption in operation.