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Ozone gas for hospital-acquired infections

Gaseous ozone in Hospitals: How effective is it against healthcare-associated infections?

Background and mechanism

Ozone (O₃) is a powerful oxidizing agent capable of inactivating bacteria, molds, and viruses through lipid peroxidation and nucleic acid damage. Its appeal in hospitals lies in its gaseous diffusion (reaching “shadow zones”) and its breakdown into oxygen after treatment. However, ozone is also a dose-dependent respiratory irritant, which requires use only in vacant, sealed, and ventilated rooms, with strict monitoring of residual concentrations.

Evidence of effectiveness

Surfaces and Rooms (Microbiological Indicators)

  • Significant log reductions (≥ 6 log₁₀) have been reported with ozone systems combined with hydrogen peroxide (H₂O₂) under controlled conditions, including activity against resistant bacterial spores.
  • Comparative evaluations of room decontamination devices conclude that ozone and H₂O₂ can achieve bactericidal levels on test surfaces, but performance varies depending on organic load, relative humidity, and room geometry.
  • Field studies (operating rooms, ambulances) show notable decreases in microbial loads in air and on surfaces after ozonation cycles (e.g., 25 ppm/30 min), though partial survival occurs depending on species and materials.

Indoor air (Microbiological indicators)

Recent work shows efficacy against bacterial aerosols in real-life conditions (2–4 log₁₀ reductions depending on organisms and exposure parameters). Viral models (murine norovirus, simian virus 40, etc.) are inactivated by 2.6–3.9 log₁₀ after 150–300 min of ozonation in specific chambers.

Hospital textiles

Emerging data (2025) suggest ozone may be effective in disinfecting hospital textiles (limiting microbial spread), but confirmation across facilities and assessments of material integrity (fiber aging, compatibility) are still needed.

Key success factors

  • Concentration, exposure time, relative humidity (RH): efficacy improves with RH (often > 60%) and adequate concentrations/exposure; shielded zones require longer cycles.
  • Combination with H₂O₂ or UV-C: platforms combining ozone + H₂O₂, or UV-C + ozone, enhance microbial reduction but add complexity in safety and validation.
  • Material/equipment compatibility: ozone may corrode or oxidize sensitive devices, so checks and protections are essential.

Practical recommendations (if a facility considers ozone)

  1. Use only in unoccupied rooms (patient rooms post-discharge, technical areas), with sealed access, sensors, and alarms.
  2. Validated local protocols: operational/qualification testing, mapping of concentrations, RH control, and confirmation of safe re-entry thresholds.
  3. Integration into a multimodal strategy: prior cleaning/detergent use, manual disinfection of high-touch points, hand hygiene, ventilation.
  4. Staff training and PPE: clear procedures for evacuation, ventilation, and cycle documentation (traceability).
  5. Clinical monitoring: if implemented, link ozone use to infection rate surveillance and process audits to assess real added value. (Gap synthesis.)

Conclusion

In hospitals, gaseous ozone shows strong microbiological efficacy on air and surfaces under controlled conditions, achieving high log reductions. It may serve as a useful adjunct for hard-to-reach areas.