How is smog measured?
The Ministry of Environment measures the air quality in Ontario using a rating scale called the Air Quality Index (AQI). The scale ranges from 0 to over 100 – the lower the AQI number, the better the air quality. The AQI is based on six key air pollutants including: sulphur dioxide, ozone, nitrogen dioxide, carbon monoxide, total reduced sulphur and particulate matter. Each hour, the concentration of the six pollutants is measured at particular stations across Ontario. There are 11 monitoring stations across the GTA. Two of those stations are located in Peel – one in Brampton and one in Mississauga – and five are located in areas bordering Peel region. The pollutant with the highest number at the given hour becomes the AQI. An AQI value between 0-15 is considered very good, between 16-31 good and between 32-49 moderate. An AQI of 50-99 is considered poor and over 100 is very poor. When the AQI is predicted to reach or exceed 50, a smog advisory is issued.
