Ottawa Downtown, Ontario PM2.5 (fine particulate matter) AQI is 21 - Ottawa Downtown, Ontario PM10 (respirable particulate matter) AQI is n/a - Ottawa Downtown, Ontario NO2 (nitrogen dioxide) AQI is 3 - Ottawa Downtown, Ontario SO2 (sulfur dioxide) AQI is 0 - Ottawa Downtown, Ontario O3 (ozone) AQI is 29 - Ottawa Downtown, Ontario CO (carbon monoxide) AQI is 2 -