Ozone in Indoor Air

Ozone is a gas that exists naturally in the upper atmosphere. At ground-level, however, ozone is a key ingredient of urban smog that is formed when sunlight reacts with other pollutants, such as nitrogen oxides and volatile organic compounds (VOCs). Most ozone in the home enters from outside. Small amounts may be released as a by-product from air purifiers or electronic equipment such as laser printers or photocopiers. Health Canada advises consumers against using products that intentionally release ozone into the air of their home.

What are the health effects of ozone?

Ozone can cause a variety of symptoms in both healthy people and people with respiratory problems, such as asthma and chronic obstructive pulmonary disease (COPD). Health symptoms include: coughing, chest discomfort, reduced lung function, shortness of breath, and irritation of the eyes, nose and throat.

What should I do about ozone in my home?

Levels of ozone in most Canadian homes are below those recommended by Health Canada. Ozone indoors is generally not a major health concern for most homeowners, and therefore, it is generally not necessary to measure ozone levels in homes.

Outdoor ozone can affect your health, and is also the major contributor to ozone levels in your home. To find out more about outdoor air quality conditions in your local area, and what steps you should take to protect your health, please consult the  Air Quality Health Index (AQHI).

Health Canada does advise consumers against using products that intentionally release ozone (known as ozone generators) into the air of their home. Ozone generators are sold as indoor air cleaners, but the level of ozone produced may be harmful to health. For more information please visit Health Canada's Consumer Product Safety website.

What are Health Canada's recommended levels for ozone?

Health Canada's Residential Indoor Air Quality Guideline for ozone recommends a maximum exposure limit of:

  • Long-term exposure: 20 parts per billion (ppb) (40 µg/m³) based on a 8-hour average

The long-term exposure limit is meant to protect against respiratory problems, such as shortness of breath, which may be caused by extended exposure to ozone.

What are the Residential Indoor Air Quality Guidelines?

The Residential Indoor Air Quality Guidelines are Health Canada's official position on the health risks posed by a specific indoor contaminant, based on a review of the best available scientific information. They summarize the known health effects, detail the indoor sources, and provide a recommended exposure level below which health effects are unlikely to occur. The Guidelines are recommendations only and are not an enforceable standard under any regulation. They are meant to serve as a scientific basis for activities to reduce the risk from indoor contaminants. This could include the development of regulations or standards or the production of communication materials aimed at the general public.

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