Microbial Ozone Decontamination of N95 Respirators: Efficacy and Material Preservation

Ozone gas is a promising method for decontaminating personal protective equipment (PPE), providing broad antimicrobial activity with minimal residue effects. However, its effects on the structural integrity and filtration performance of N95 respirators are not well established. This study evaluated the antimicrobial efficacy of ozone treatment against Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans on culture media and N95 respirators, and assessed whether fiber integrity and filtration efficiency were preserved using the GermZero3 prototype sterilizer developed with the National Science and Technology Development Agency (NSTDA). Microbial suspensions (10⁴ CFU/mL in TSB broth) were inoculated onto agar plates and respirator sections, and then exposed to 25–50 ppm ozone for 15–60 min. Viability was assessed by culture, while fiber integrity and filtration efficiency were evaluated by scanning electron microscopy and a NaCl aerosol test. Complete eradication of P. aeruginosa was achieved after 15 min and S. aureus within 45 min. C. albicans showed 99.90–99.98% reduction by 45–60 min, with no statistically significant difference from full clearance. When applied to contaminated respirators, ozone treatment eliminated all three pathogens after 60 min. Fiber morphology remained intact, and filtration efficiency was preserved at 99.99%, exceeding the ≥95% N95 standard. These findings support ozone treatment with the GermZero3 sterilizer as a safe and effective method for extending N95 respirator use during shortages.