HVAC issue in CT 1

I had a client not too long ago that has a type 1 (or level 1) mold issue in the basement. There's a secure bulkhead and an open stair well to the stairs up to the apartments.

The problem is tha the duct to the window for the ventalation is open. There's a grate on the outside. One vent coming stright down out of the window to about 2 feet from the floor. The second comes straight out at window/ceiling level. The idea is for the warm air to escape through the top vent and colder air from the outside is to come through the bottom vent opening closer to the floor in order to then travel, stir up air away from the furnace and then heat, and escape out the top. Simple right?

Yes, simple, however creating some complications. Apparently there are large piles of leaves and other outside material that has found it's way through the grate into the basement. Which leaves me to beleve that the moist air is coming in through the vents as well. Trying to do research has lead me to noting. Most vents on the furnace are carried through normal ducts to the outside, keeping the circulation in a close ciruit between the ouside and the furnace....right?

Besides having a water issue which will be corrected by installing the Grate Products System I can't see where else the moisture could be coming from. Even having a Santa Fe working full tilt couldn't eleminate an endless stream of moisture from the outside.

I'm vexed by the idea. I don't want them to install and then still experience mold because of the outside. I'll have pictures and I'll have information before anything happens..That's for sure.