Few months back, I've bought 11 rack systems for 2 different storeroom locations. The untreated MDF boards then starts to mold. The molds are like evolving into miniature forests. I had to remove ALL items, wipe them down, paint with elastomeric paint on all sides, board by board. 11 racks*4 boards = 44pcs. Now they're all fine.. Pheww..