ProtoxHysan is a disinfectant - that is, it kills the mold and washes the surface. However, as ProtoxHysan leaves no residue of the active ingredient, it has no preventive effect.
If there is a risk of the mold coming back, you should perform a preventive treatment with ProtoxMold after cleaning with ProtoxHysan. In addition, the moisture source should be identified and removed before fighting the mold infestation.