A number of industrial hygienists have expressed opinions that the use of ozone by restoration contractors is unsafe and should not be used. The problem is that many fire and smoke restoration companies use ozone to remove odors, despite being warned of these problems in their own trade journal.
A 2022 article published by Restoration & Remediation Magazine, Using ozone in fire recovery: Is it friend or foe?states:
Are there health risks associated with using ozone?
Most of my colleagues in the restoration industry believe that ozone is natural to our environment and relatively harmless. To illustrate this, here are some comments from an ozone generator manufacturer: ̵6;Ozone is a very effective natural sterilizer capable of inactivating virtually all organic contaminants on contact. Being a highly reactive gas, ozone continuously returns to its most stable form by releasing one of its atoms to convert to oxygen (from O3 to O2). Since ozone is a gas composed entirely of oxygen, it leaves no chemical residue whatsoever. The only byproduct that remains is fresh, clean air.
That sounds pretty amazing, doesn’t it? Let’s take a closer look and see what scientists and government agencies have to say about ozone.
The Canadian Center for Occupational Health and Safety reports that: ‘Even very low concentrations of ozone can be harmful to the upper respiratory tract and lungs. The severity of the damage depends on both the concentration of ozone and the duration of the exposure. Serious and permanent lung damage or death can result from even very short-term exposure to relatively low concentrations.’
The US Environmental Protection Agency states that ozone exposure can be particularly dangerous for people who have respiratory conditions such as asthma and COPD. People with asthma are likely to be affected by ozone in two ways: (1) They may be more sensitive to ozone than other people and experience lung function changes and respiratory symptoms at lower concentrations or to a greater extent; and (2) the damage, inflammation, and increased airway reactivity induced by ozone exposure can exacerbate a person’s underlying asthma.
The National Institutes of Health has identified the following health effects associated with ozone exposure:
- Nervous system disorders: Effects on the nervous system other than anesthesia
- Respiratory effects other than irritation: Cumulative lung damage
- Respiratory effects: Acute lung damage/edema or other
- Irritation: Eyes, nose, throat, skin
The article ends with the following warning:
If you are going to use ozone generators in indoor environments, take the necessary precautions to protect workers and passengers. Consider the following:
- Give passengers and workers an ozone safety data sheet so everyone is informed.
- Remove or protect any objects or materials that may be adversely affected by ozone exposure.
- Set up appropriate environmental controls and place warning signs around the area where ozone will be used.
- Provide workers with appropriate personal protective equipment and avoid working in areas where ozone is generated.
- After the ozone treatment is complete, ventilate the area thoroughly before allowing workers to re-enter.
Conduct air testing after ozone use to verify ozone levels are safe and no toxic chemicals or byproducts remain.
The real question is whether fire and smoke restoration companies should be doing this at all. Science suggests that the levels of ozone needed to effectively remove odors create an unsafe structure during and after the process is complete.
The United States Environmental Protection Agency addressed this point by stating in a study, Ozone generators sold as air purifiers:
Are ozone generators effective in controlling indoor air pollution?
Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove pollutants from indoor air.
Some manufacturers or suppliers suggest that ozone will render nearly all chemical pollutants harmless by producing a chemical reaction whose only byproducts are carbon dioxide, oxygen, and water. This is misleading.
- First, a review of scientific research shows that for many of the chemicals commonly found in indoor environments, the reaction process with ozone can take months or years (Boeniger, 1995). For all practical purposes, ozone does not react at all with such chemicals. And contrary to specific claims made by some vendors, ozone generators are not effective in removing carbon monoxide (Salls, 1927; Shaughnessy et al., 1994) or formaldehyde (Esswein and Boeniger, 1994).
- Second, for many of the chemicals with which ozone readily reacts, the reaction can form a variety of harmful or irritating byproducts (Weschler et al., 1992a, 1992b, 1996; Zhang and Lioy, 1994). For example, in a laboratory experiment that mixed ozone with chemicals from new carpets, ozone reduced many of these chemicals, including those that can produce new food odors. However, in the process the reaction produced a variety of aldehydes, and the total concentration of organic chemicals in the air increased rather than decreased after the introduction of ozone (Weschler, et. al., 1992b). In addition to aldehydes, ozone can also increase indoor concentrations of formic acid (Zhang and Lioy, 1994), both of which can irritate the lungs if produced in sufficient quantities. Some of the potential byproducts produced by ozone’s reactions with other chemicals are inherently highly reactive and can produce irritating and corrosive byproducts (Weschler and Shields, 1996, 1997a, 1997b). Given the complexity of the chemical reactions that occur, further research is needed to more fully understand the complex interactions between indoor chemicals in the presence of ozone.
- Third, ozone does not remove particles (such as dust and pollen) from the air, including the particles that cause most allergies. However, some ozone generators are manufactured with an “ion generator” or “ionizer” in the same unit. An ionizer is a device that spreads negatively (and/or positively) charged ions in the air. These ions attach to particles in the air and give them a negative (or positive) charge so that the particles can attach to nearby surfaces such as walls or furniture, or attach to each other and settle out of the air. In recent experiments, ionizers have been found to be less effective at removing particles of dust, tobacco smoke, pollen, or fungal spores than either high-efficiency particulate filters or electrostatic filters. (Shaughnessy et al., 1994; Pierce, et al., 1996). However, it is clear from other experiments that the effectiveness of particulate air cleaners, including electrostatic precipitators, ion generators, or pleated filters, varies widely (US EPA, 1995).
There is evidence to show that at concentrations not exceeding public health standards, ozone is not effective in removing many odor-causing chemicals.
The bottom line is that many people in the fire and smoke abatement industry use these machines that use ozone to remove the smell of smoke. The manufacturers that sell these ozone machines want to keep selling them. The trend is that industrial hygienists express opinions that we should stop using this method because it is not safe and refer to scientific articles to prove their views.
Where are the scientific articles that support smoke removal by these ozone machines is safe? I couldn’t find them.
Leadership is required to improve safety.
– Jackie Stewart