Some Products Emit Harmful Levels of Ozone

This page created June 23, 2016

image of products that emit ozone

The California Air Resources Board (ARB) staff recently published a study to measure ozone emissions from 17 consumer products and home appliances. They found that five products in three categories produced ozone at levels that may result in potential health effects.

Ozone is a reactive gas comprised of three oxygen atoms. While ozone high up in the atmosphere protects us from the sun's harmful rays, at ground level, ozone can cause adverse health effects such as coughing, chest tightness and shortness of breath. Exposure to ozone may both induce and worsen asthma symptoms and worsen lung disease; it might also increase the risk of premature death. Some consumer products and home appliances are designed to emit ozone either intentionally, or as a by-product of their functions.

Study Findings

graphic showing personal exposure concentrations for different products

Products that were found to emit harmful levels of ozone included a residential ozone laundry water treatment appliance, two fruit and vegetable washers, and two facial steamers. Use of some of these products increased ozone concentrations in a small room to concentrations that exceeded the level of 1-hr California Ambient Air Quality Standard (CAAQS) for outdoor ozone (0.09 parts per million [ppm]). The greatest increase of room ozone concentrations during typical use of the products resulted from use of the laundry water treatment system. During one wash cycle, this product increased the room ozone concentration by an average of 0.11 ppm.

Due to users' close proximity to this product, the concentration of ozone that users might actually be exposed to (the personal exposure concentration) can be even higher than the room concentrations measured. Personal exposure concentrations that resulted from one use of some products tested are shown above. It shows that during one wash cycle, users of the laundry water treatment system may be exposed to an average of 0.42 ppm ozone potentially for 1 hour. This level of exposure is equivalent to about one-quarter to one-half of the ozone that a typical California resident may be exposed to in one day.

For some products, one use does not increase the room ozone concentrations markedly, but repeated use can result in high personal exposure concentrations for the user. For example, when a fruit and vegetable washer was used for three continuous wash cycles with reused water, the average personal exposure concentration was 2.55 ppm, over 28 times higher than the level of the 1-hr CAAQS. For the remaining products tested, their average ozone emissions were low, but surprisingly high peaks were commonly observed. When using a facial steamer with an ozone-emitting ultraviolet (UV) bulb, for example, peak ozone levels as high as 1.1 ppm were reached. Such exposures may raise concerns for sensitive populations, such as people with respiratory diseases, and for those who use these products often. It should be noted that most of the products tested in this study are used only briefly; thus, their impacts on indoor air quality and exposure are limited to shorter time periods compared to continuously operating products such as ozone-generating portable air cleaners.

Ozone from Other Products

In addition to the products tested in this study, some air cleaning devices have been found to increase indoor ozone concentrations to harmful levels. In September 2007, ARB adopted a regulation (California Code of Regulations, Title 17, §94800 - §94810) to limit the ozone concentrations from indoor air cleaning devices to no more than 0.050 ppm. More information about the regulation may be found on our fact sheet about the regulation.

Exercise Caution When Buying or Using Ozone-Generating Products

There are no consumer product regulations that limit ozone emissions from products similar to those tested in this study. Therefore, consumers should exercise caution when purchasing or using such products:

  1. Avoid using products that emit ozone intentionally (ozone generators), and exercise caution when using products that may emit ozone as a by-product of their functions. Read user manuals carefully to determine if a product can emit ozone. Some manufacturers explicitly indicate their products emit ozone, but others may use different words, such as "super oxygen", "super oxygenated", "saturated oxygen", "activated oxygen", "trivalent oxygen", "energized oxygen", "allotropic oxygen", "mountain-fresh air", or similar phrasing for ozone. Be cautious about products that have electrostatic precipitators, ionizers, corona discharge units, plasma generators, or UV bulbs, because they have the potential to generate high concentrations of ozone.
  2. If you still wish to use products that may emit ozone, only use them when the space is not occupied by people and has proper ventilation.
  3. For the categories of products discussed above, check our list of Potentially Harmful Ozone-Emitting Products, and avoid using these products, which are advertised as emitting ozone.

More Information

For more information regarding this study, you may wish to view our press release and fact sheet about the study. You can also read the article published in the journal Indoor Air for more detailed results. If you have any questions regarding this study or the information on this page, please email