Are you positive the subfloor is particle board? Are there more than one layer of sheathing over the joists? What are they and thickness of each. Particle board has not been used as a subfloor for many years once it was learned it's junk for that purpose.
Let us know before you make a move.
Tile 4 You LLC Troy, MI
DITRA Installs - KERDI Watertight-Mold-Free Showers. I have NEVER made a mistake, I thought I did ONCE, but, I was WRONG!A+ BBB rating - est. 1987 - over 50 yrs. exp.