The Practical Application of Ozone Gas as an Antifungal (Anti-mold) Agent

Background

Mould and fungal contamination in enclosed spaces - homes, hospitals, food storage areas and other buildings - is difficult to eliminate using conventional liquid disinfectants and manual cleaning alone, because these methods struggle to reach every crevice, cavity and hidden surface in a room. Researchers have long looked at gaseous ozone as an alternative, since it can spread through an entire sealed space, including areas that are hard to access physically, without needing surfaces to be manually scrubbed.

Study design

Researchers James B. Hudson and Manju Sharma tested a portable ozone generator (the Viroforce 1000 system) against a panel of thirteen different fungal species associated with indoor mould contamination. Fungal samples were prepared as either wet or dried films on test surfaces and then exposed to ozone gas, generated at a concentration of around 35 parts per million (ppm) for 20 minutes, combined with a short burst of high relative humidity (over 90%). Some samples underwent one treatment cycle, others two. Testing was carried out under controlled laboratory conditions and also under simulated field conditions on a range of real-world surface types, with effectiveness measured by the reduction in viable fungal colony-forming units (CFU) recovered after treatment.

Findings

The ozone treatment reduced viable counts by around 3 log10 CFU (roughly a 99.9% reduction) for most of the fungal species tested, under both laboratory and simulated field conditions. Ozone concentrations in the treated space returned to normal background levels within 15-20 minutes after the active treatment phase, and the entire cycle, including this clearance period, took under one hour from start to finish.

What the authors concluded

The authors concluded that the ozone generator tested was both safe and practical as a decontamination tool for mould in buildings. They highlighted that gaseous ozone can penetrate every part of a sealed room, including sites that are difficult to reach with conventional liquids and manual cleaning, and that the system could be switched on and off remotely once a room had been made airtight, with a fast return to safe ambient ozone levels after treatment.

Limitations of this study

This work tested a single specific device (the Viroforce 1000) at one ozone concentration and humidity combination, so the results may not generalise to other ozone equipment, doses or exposure times. Fungal films prepared for laboratory and simulated field testing may not fully replicate the way mould becomes embedded in real building materials over long periods, where ventilation, porosity and moisture conditions vary widely. The published study also does not detail longer-term monitoring of treated spaces or health outcomes for occupants, and rooms must be vacated and sealed during treatment. Some bibliographic details for this 2009 paper, including the exact publication date and page numbers, could not be independently confirmed from openly accessible sources at the time of writing, though the title, authors, journal, volume/issue and DOI were verified against the publisher's listing and independent academic databases.