Bathroom Remodel -- Mold?

[William Schuster]

Hey all, 

Was asked by my parents to demo out their bathroom in prep of a remodel. My concern is though that the shower leaked for a few years before they stopped using it. I am worried about the amount of mold I may find. 

Does anyone have a recommendation on the type of respiratory protection I should use? I was not going to trust the cheap face masks with what I'm worried about is down there.

Appreciate any advice you can offer.