Advice from BuRO on the health risks of ozone emissions from air purifiers

Have a health warning applied to products on the market that generate ozone in quantities that represent a health risk. For small spaces (up to 2.4 m3), the maximum ozone emission is 0.3 mg per hour, for other spaces the maximum ozone emission is 3 mg per hour. This is the advice from the Office for Risk Assessment & Research (BuRO) to the Inspector-General of the NVWA.


Additional advices from BuRO to the Inspector-General of the NVWA:

  • Actively communicate on the NVWA website about the risks of consumer products that emit ozone.
  • Advise consumers to no longer use these products, or to only enter the space following a long period of ventilation.

BuRO advises the minister of Public Health, Welfare and Sport (VWS):

  • Consider for the transition period, in which in situ generated ozone in the Netherlands is exempt from the Plant Protection Products and Biocides Act, banning in situ generated ozone in applications in which there is direct exposure of consumers through inhalation.

Reason for investigation and research questions

The background to this investigation was a question from a consumer to the NVWA about an air purifier for use around the cat litter tray, with a reported ozone emission of 25 mg per half hour. Due to the absence of a legal standard for ozone emissions from consumer products, the Enforcement Directorate of the NVWA submitted the following questions to BuRO:

  • What is the health risk of consumer products that generate ozone?
  • What is the maximum acceptable emission of ozone from consumer products so that this standard can be used for supervision and enforcement? In supplying your answer, take into account the variation in the spaces in which the product is used.


BuRO asked the RIVM/WFSR Front Office Food and Product Safety (FO) to perform an assessment of the health risks from ozone emission. The status of ozone as a biocide was investigated. Moreover, FO was asked to perform an online market survey into air purifiers that emit ozone, and on the basis of the ozone emission notified by the manufacturer, to perform a calculation of the expected ozone concentration in the air. Finally, FO was asked to calculate the maximum permitted ozone emission that results in no health risk.

BuRO also performed a literature study into air purifiers based on ozone and into the dose-effect relationship of ozone. BuRO wrote this advice on the basis of the FO assessments and literature study.

Answers to questions

The following answers emerged from the research:

  • Ozone is a strong oxidizer that has antibacterial and antiviral properties. Ozone can cause irritation of the airways. In the event of long-term exposure, this can lead to respiratory problems, the occurrence of asthma in children and an increase in respiratory effects in asthma patients. The health-based guidance value for ozone is 40 µg/m3.
  • At present, ozone generated in situ is exempted in the Netherlands from the Plant Protection Products and Biocides Act. In June 2023, at EU level, ozone was approved as an active substance. In the subsequent phase, authorisations can be applied for at national or European level for the individual biocides based on in situ generated ozone. This will take about 5 years. After that, in situ generated ozone is expected to be no longer allowed in places accessible to consumers.
  • The majority of air purifiers from the online market survey result in an ozone concentration that considerably exceeds the health-based guidance value of 40 µg/m3. For small spaces (up to 2.4 m3), the maximum ozone emission is 0.3 mg per hour, for other spaces (from 20 m3) the maximum ozone emission is 3 mg per hour.