Ozone

Find out about ozone, its sources and health risks.

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About ozone

Ozone (O3) is a gas that exists in the upper atmosphere and at ground level.

It can be good or bad for your health depending on its location.

Ozone is a naturally occurring gas that is present in the upper atmosphere. It is necessary for life on earth. The ozone layer keeps the planet warm and protects us from the sun's ultraviolet rays.

Ozone can also be formed at ground level when sunlight interacts with pollution. This type of ozone (ground-level ozone) is a key component in urban smog. It can enter your home and pollute indoor air.

Indoor sources of ozone

Most of the ozone in homes comes from the outside. The level of ozone indoors is generally lower than the level outdoors.

Health effects of ozone

Ground-level ozone can cause a variety of health effects, including:

  • coughing
  • irritation of the:
    • eyes
    • nose
    • throat
  • chest discomfort
  • shortness of breath
  • decreased lung function

You are more sensitive to ozone if you have an underlying breathing condition.

How to reduce exposure to ozone in the home

You can reduce ozone levels in your home by:

  • using an air conditioner instead of opening windows when ozone is at its peak (usually in the afternoon)
  • avoiding ozone generators

Canada advises against using ozone generators in homes. They are sold as indoor air cleaners, but the level of ozone they produce may harm your health. They also create other dangerous chemicals.

Consult the air quality health index to learn about:

  • outdoor air quality conditions in your area
  • steps you can take to protect your health from outdoor ozone and other pollutants

Canada’s recommended exposure limit for ozone

Canada has developed an indoor air quality guideline for ozone in homes. The guideline recommends a maximum limit for long-term exposure (over days or years).

This limit protects against breathing problems that long-term ozone exposure may cause.

Ozone levels in Canadian homes are typically below the recommended limit and are therefore not a health concern for most homeowners.

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