Ozone is frequently marketed for mold treatment and the claim that it kills mold appears in many places. The reality is more nuanced — and understanding exactly what ozone does and does not do for mold is essential to using it correctly.

What Ozone Does to Mold

Ozone is a powerful oxidizing agent that reacts with and damages the cellular structures of mold. Laboratory research demonstrates that ozone can kill mold spores and mold colonies on exposed surfaces at sufficient concentrations. What the research also shows: ozone penetration into porous materials is limited. It effectively kills mold on surfaces it directly contacts but does not penetrate deep into drywall, insulation, or wood framing where significant mold growth occurs in water-damaged buildings.

What Ozone Cannot Do for Mold

• Ozone cannot remediate mold in structural materials — mold growing inside drywall or in insulation is not effectively reached by ozone at concentrations safe for the structure
• Ozone cannot address the moisture source — if moisture is still present, mold will regrow on treated surfaces
• Ozone treatment is not a substitute for professional mold assessment

What Ozone Is Effective For in Mold Situations

• Surface mildew on non-porous or low-porosity surfaces — kills surface mold effectively
• Residual airborne mold odor after professional mold remediation is complete — effective as a finishing step
• General musty odor in a space that has been properly dried and cleaned

The Correct Use of Ozone for Mold-Related Odor

Ozone is the right tool for the last step — not the first step. The sequence: identify and fix moisture source, extract water and aggressively dry, professional mold assessment if growth is suspected in structural materials, professional mold remediation if confirmed, confirm moisture levels are normal, then ozone or hydroxyl treatment to address residual airborne mold VOCs.