Particleboard refers to recycled chip wood. It's underneath the tiles of floors or walls, in mobile homes, and as the basis for cheap furniture such as bookcases and desks. Because particle board contains formaldehyde, a toxic substance, sealing the board--even if you plan to tile over it--is a wise decision, so that you can cut yourself off from possible noxious fumes. Sealing particleboard can also make this often industrial-looking board seem more aesthetically pleasing.
Vacuum the floor thoroughly. Combine 1/2 gallon water with 1/2 gallon white vinegar in a large bucket. Dip the very tips of a broom in the mixture and use the broom to wipe down the floor.
Apply the broom to the floor slowly, working in small sections, drying each section immediately with a clean, dry mop, before moving on to the next section. Pat down the entire floor with paper towels and allow it plenty of time to air-dry.
Pour sealer especially for particleboard into a paint roller pan. Dip your paint roller in the sealer and apply a light coat to the floors, starting at the far end of the room and working your way back. Allow the sealer to dry and apply a second coat.
It is important to select a sealer especially for particleboard that blocks toxic emissions. Read labels carefully.