When a USian speaks of "particle board", is that the same as what we in the UK would call "chip board" (coarse stuff, commonly used for flooring) or "fibre board" (furniture, shelving and similar)?
Fibre board comes in light, medium and high density: LDF, MDF and HDF, though you seem to have search for LDF/HDF. HDF sounds like (er, pun not intended) the really dense stuff being advocated, as MDF is pretty solid even unvarnished.