Lowering of SO2 air quality standards

On March 20, 2018, the MECP confirmed its regulatory proposal to change the sulphur dioxide (SO2) air standards over a five year phased-in period.

The changes lower the regulatory standard for SO2 from the previous 1 hour standard of 690 µg/m3 to 100 µg/m3, while the previous 24 hour standard (275 µg/m3) has been eliminated. However, there is the introduction of a new, annual standard of 10 µg/m3.

In relation to SO2, the MECP is also clarifying that equipment start-up/shut-down operating scenarios are to be included in the assessment for regulatory modelling. Sources of most concern tend to be flaring stacks at petroleum refineries.

For more information on the possible implications of the change in the air standard and your air compliance status, contact Farida Dehghan Ph.D., P.Eng. at ext. 110, or fdehghan[at]