Because this barrier method does not automatically & periodically provide water to replenish the trap seal, it must provide a barrier on the inlet side of the trap seal that will minimize evaporation caused by the ambient air on the building side of the trap. This barrier must also provide adequate drainage capabilities required for the floor drains intended use as determined by its design, size & installation location. While developing the requirements & tests for these devices, certain adverse conditions were taken into consideration: introduction of fouling substances such as dirt/sand, floor wax or grease into the device. Drainage requirements are provided to accommodate infrequent & sizeable water flows caused by water line breaks, fixture overflows or backflow preventer discharges.