As of May 1, 2000, as part of its new Air Quality Ontario initiative, the ministry provided earlier, more effective notification of poor air quality than ever before.
When air quality and weather conditions are likely to produce smog, the ministry takes steps to inform the public, and warn those most vulnerable to the health impacts of poor air quality. It provides two levels of alert:
- A Smog Watch is issued when there is a 50 per cent chance that elevated smog levels are forecast to occur within the next three days.
- A Smog Advisory is issued when there is a strong likelihood that elevated smog levels are forecast to occur within the next 24 hours, or it can be issued immediately if widespread, poor AQI readings occur, and weather conditions conducive to the persistence of such levels are expected to continue for several hours.
When the weather changes, resulting in cleaner air, the ministry issues an advisory termination notice.
In May 2001, the ministry adopted the policy of issuing a smog advisory immediately if widespread, poor AQI readings occur, and weather conditions conducive to the persistence of such levels are expected to continue for several hours.
As of August 2002, the ministry added fine particulate matter (PM2.5) to its AQI. This new sub-index provides Ontarians with more information on air quality so they can make informed decisions to protect their health and help improve the air we all share.