A quick web search on “ozone generator” returns more than 14 million results. Amongst the obligatory sponsored content showing various products selling for as low as 400 DKK (50 €), some linked pages refer to articles warning specifically against ozone generators designed for personal usage. Some of those pages come from governmental sources, such as the United States’ Environmental Protection Agency (EPA). But, why are household ozone generators generally non-recommended and seen as hazardous? How different are they from industrial-purpose generators? And, how are surface disinfection devices using ozone such as STERISAFE PRO comparable (or not) to basic ozone generators?

Ozone generators and safety

The most important parameter to consider when using ozone – for any purpose – is safety. Ozone is a known and registered biocidal agent and as such, can be extremely hazardous. The generally accepted thresholds for ozone exposure are as follow (values from the United States’ Occupational Safety and Health Administration, OSHA):

Light work, < 8h:             0.1 ppm

Short-term, < 15 min      0.3 ppm

Immediately dangerous
to life and health (IDLH):  5.0 ppm

When advertising for their ozone generators to be used as household air purifiers, some manufacturers take great liberty with their claims, and imply that their device can effectively remove bad odours, harmful pathogens or particles. However, often these claims can be debatable at best, if not erroneous. The reason for this is that ozone needs to reach certain concentrations and certain contact times for efficiently removing bad odours and/or to have a significant antimicrobial effect.

Previous studies performed in particularly malodorous environments such as farms reported that at lower concentrations, ozone was only effective at removing part or selected groups of foul-smelling compounds (Kim-Yang et al., 2005; Watkins et al., 1997). The authors suggested that greater reduction of smelling compounds would occur only at ozone levels higher than permissible exposure limits. Moreover, ozone can impair one’s sense of smell, and the sensation of freshness after using a household ozone generator would be mostly due to a masking effect rather than a removal effect (California Air Resources Board, 2020).

The same would apply to the biocidal efficacy of ozone. While ozone is a well-known powerful oxidizing agent that can destroy a broad spectrum of microorganisms, efficacy is highly dependent on several factors, including (1) ozone concentration, (2) contact time between ozone and targeted microorganisms, and (3) inherent resistance of the targeted microorganism. This is why having efficacy tests and reports from third-party laboratories (hyperlink) is paramount to ensure that ozone is used properly and for the reasons specified. Vague claims from manufacturers with no 3rd party verification can lead to improper use of ozone and consequences on human health.

In short, it is imperative for any ozone-based equipment to provide to their customers clear information on safety measures, scope of usage, and properly documented claims. Unfortunately, a great number of manufacturers for household generators and the likes fall very short from these requirements. STERISAFE PRO operates at ozone levels high enough to guarantee full efficacy; in addition, safety training gives the end-users every tool needed to ensure that no one, at any point, enters in direct contact with dangerous levels of ozone.

STERISAFE PRO in not just another ozone generator, but integrates room monitoring, cloud service, data reporting and superior efficacy in a radical new technology for surface disinfection.

Guarantees of STERISAFE PRO

From a technical standpoint, STERISAFE PRO is equipped with several components that makes it much more than a simple ozone generator, and that ensures that every disinfection cycle is carried out effectively and most importantly, safely. Moreover, training courses given to future users ensure that all safety measures are respected and that the equipment is used as intended.

One of the key aspects of STERISAFE’s Full-Depth Disinfection Cycle (FDDC) is the real-time, constant monitoring of the ozone concentration in the sealed, disinfected room. Because it is important that no one be in contact with ozone at any time during the disinfection process, the STERISAFE PRO is equipped with an optic-based ozone monitor, which updates at regular intervals and ensure that the disinfection cycle is progressing under the proper conditions to ensure full efficacy. This information is relayed to the wireless control tablet, so the operator can follow the progress of the cycle with real-time information.

The similar sensor feedback loop is used to monitor the humidity in the room at all times. Indeed, humidity level is known to be directly related to the antimicrobial reaction of ozone. More particularly, a higher relative humidity allows for a better reactivity of ozone (Li & Wang, 2003). This synergy makes ozone concentration [O3] and relative humidity %RH the most important parameters for antimicrobial activity. While levels for both parameters are pre-determined by extensive research regarding efficacy, a real-time monitoring function is imperative to ensure that every cycle is conducted appropriately and without issue.

Equally important to the constant monitoring is the ability to produce ozone on a reliable manner and without by-products. To do this, the STERISAFE PRO uses an oxygen concentrator, which produces ozone from oxygen purified from ambient air. Having this intermediary step permits not only a stable, high throughput of ozone (approx. 40 g/h), but also removes naturally occurring nitrogen from the ozone production step. This ensures that no harmful nitrogen oxides (NOx) gases – a family of common air pollutants – are released along ozone, which is a common problem amongst not well-thought, air-fed ozone generators.

But co-production is not the only source of potentially harmful by-products. Like all disinfectants, ozone can react with organics compounds, producing what are called disinfection by-products (DBPs). Moreover, disinfection processes can cause the formation of particulate matter (PM), which are also considered harmful due to their small size and damage they can cause upon inhalation. Such particles are also a common consequence of the reaction between ozone and volatile compounds. To address this issue, the STERISAFE PRO is equipped with an Electrostatic Precipitator (ESP), whose role is to trap and collect such particle at the end of every cycle. Manufacturers typically ignore this issue, and lower-end ozone generators systematically cause a surge in airborne particle concentration. More details on this process can be found in a previous STERISAFE white paper.

Beyond the presence of such components that determine the quality – or lack of – of an ozone-based solution, manufacturers should be able to provide full documentation to support and back their claims. For disinfecting services such as STERISAFE PRO, this includes registering at a European level under the Biocide Product Regulation, and testing their products against the most adapted and recognized standards available. Ideally, only products that have gone through such thorough quality testing and vetting by competent authorities should be able to enter the market. Unfortunately, in the world of ozone-based solutions, this is far from being the case.


The sole use of ozone is very far from being a guarantee of efficacy and quality. On the contrary, using ozone incorrectly could be extremely hazardous and potentially cause serious health problems.  STERISAFE is proud to uphold the highest standards when it comes to its products, from their production up to their usage. Moreover, STERISAFE’s Full-Depth Disinfection Cycle (FDDC) is protected through a comprehensive Intellectual Property (IP) coverage, and patent applications are issued in several countries across the world (European patent #: EP2806903).


  1. Li CS & Wang YC (2003). Surface germicidal effects of ozone for microorganisms. American Industrial Hygiene Association Journal 64:533-537
  2. Kim-Yang, H., Von Bernuth, R. D., Hill, J. D. and Davies, S. H. (2005). Effect of ozonation on odor and the concentration of odorous organic compounds in air in a swine housing facility. Transactions of the American Society of Agricultural Engineers 48(6):2297–2302.
  3. Watkins, B. D., Hengemuehle, S. M., Person, H. L., Yokoyama, M. T. and Masten, S. J. (1997). Ozonation of swine manure wastes to control odors and reduce the concentrations of pathogens and toxic fermentation metabolites. Ozone: Sci. Eng. 19(5):425–437.
  4. California Air Resources Board (2020). Hazardous Ozone-Generating “Air Purifiers”. https://ww2.arb.ca.gov/our-work/programs/air-cleaners-ozone-products/hazardous-ozone-generating-air-purifiers
  5. EPA, United States Environmental Protection Agency (2019). Ozone Generators that are Sold as Air Cleaners. https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners