This content is intended for the public covered by the exceptions of the Charter of the French language and its regulations. If you read on, you confirm that you fall within one of these exceptions.
The Air Quality Index (AQI) is an information and awareness tool designed to inform the public about air quality in Québec.
Access to AQI map
(in French only) 
The AQI measured at stations in the City of Montréal is not included in the map. To consult it, visit the
City of Montréal website
.
The AQI results are grouped into three categories. Health and environmental citizenship messages enable users to adapt their activities to the conditions observed.
| Category | Health message | Eco-civic message |
|---|---|---|
 Good (1-25) |
Fully enjoy your outdoor activities. | Everyone can help maintain good air quality. Use active and less polluting transportation (walking, cycling, metro, bus, train, carpooling) and limit the use of your fireplace or wood stove in the winter. |
 Acceptable (26-50)
|
Air quality is acceptable for most residents. There are few health risks. | |
 Poor (51+) |
The general public should not experience any significant health effects. However, the most vulnerable individuals may
be affected, such as young children, seniors and people with respiratory or cardiac problems. For this reason, it is recommended that they reduce their physical
activities outside. See the list of
health effects of air
pollution for more information. |
Grey dots indicate that data for the station is not available at this time.
AQI results are influenced by human factors (sources of air contaminant emissions) and natural factors (weather conditions and topography). The influence of all these factors is specific to each AQI monitoring station.
The air quality index (AQI) presents the conditions observed every hour of the day at the stations of the Réseau de surveillance de la qualité de l’air du Québec (in French only). Each point on the map represents a station. They are divided into two groups, based on their representativeness: urban or regional.
Urban stations produce data with limited spatial representativeness due to the many sources of emissions in densely populated areas. In general, if you live in a municipality where there is a station, it will be a good indicator of air quality for the entire urban environment.
Regional stations produce data with greater spatial representativeness, as they are located in areas far from emissions sources. Generally, they are representative
of regional background levels. If there are no stations near you, refer to the nearest regional station or
air quality forecasts
from the Info-Smog program. They will be good indicators of the air quality in your area.
Station locations are chosen according to the objectives of the Réseau de surveillance de la qualité de l’air du Québec (in French only).
All the details can be found on the annual air quality index statistics page.
Each hour, the AQI at a station is calculated using the sub‑index values of each available contaminant (ozone, particulate matters, sulfur dioxide, nitrogen dioxide and carbon monoxide), based on the following equation:
Sub‑index = (measured concentration/reference value) x 50
The reference value for a contaminant is the concentration at which air quality is considered “poor.” This value is determined on the basis of criteria to protect human health. The reference values are as follows:
| Contaminant | Type of Measurement | Reference Value |
|---|---|---|
| Ozone (O3) | Hourly average | 82 ppb |
| Particulate matter (PM2,5) | Average over three hours | 35 µg/m³ |
| Sulfur dioxide (SO2) | Maximum over four minutes1 | 200 ppb |
| Nitrogen dioxide(NO2) | Hourly average | 213 ppb |
| Carbon monoxide (CO) | Hourly average | 30 ppm |
1 Maximum 4-minute average concentration over a given hour.
The AQI at the station is determined by the highest sub index value. This result is then rounded to the nearest integer and categorized as good, acceptable or poor. For each station, the map presents the detailed result with the value from each available sub index, as well as their measured concentration.
The AQI is calculated using unvalidated data for the contaminant available at each station, among the five possible contaminants. Validated results may therefore differ slightly. Almost all stations are minimally equipped with PM2.5 and O3 analyzers.
For more information, contact us at: infoair@environnement.gouv.qc.ca.
