Overview

Because air dispersion models are constantly evolving as new science becomes available, the ministry developed an implementation plan for model version updates to ensure we continue to use the best available science, and to provide clarity and consistency to the regulated community and stakeholders. This implementation plan was developed with input from stakeholders.

Key elements of the plan include the following:

  • Monitoring and assessing developments related to regulatory model updates on an ongoing basis and discussing with stakeholders, as required.
  • Notifying stakeholders each year, approximately 6 months in advance, whether updated model versions are planned for adoption. This gives facilities time to determine if they will be affected by model updates and if so, to contact their local district office for assistance in developing a path forward, as needed.
  • Where updated model versions are planned for adoption, posting an information notice on the Environmental Registry approximately 6 months following pre-notification to formally adopt the updated model versions. We may adopt updated model versions annually as necessary.
  • Updating regulatory data files, instruments and guidance materials to reflect the adoption of updated model versions, as necessary.

Compliance approaches under O. Reg. 419/05

Ontario’s local air quality regulation (Ontario Regulation 419/05: Air Pollution – Local Air Quality) under the Environmental Protection Act is part of the province’s air management framework. It regulates air contaminants released into communities by various sources, including local industrial and commercial facilities.

The regulation includes 3 compliance approaches for industry to demonstrate environmental performance and make improvements when required. Industry can:

  • meet the air standard
  • request and meet a site-specific standard
  • register and meet the requirements under a sector-based technical standard (if available)

Most Ontario facilities are regulated by the air standards compliance approach (that is, they meet the air standard), although all 3 approaches are allowable under the regulation.

Models are part of the air standards and site-specific standards compliance approaches.

Approved models and meteorological data

Section 6 of Ontario Regulation 419/05 provides a list of approved dispersion models for use in assessing compliance with air standards or site-specific standards under the regulation. Currently, the approved dispersion models are:

  1. The AERMOD dispersion model (version 24142) available from the Ministry of the Environment, Conservation and Parks (MECP).
  2. The ASHRAE method of calculation. Section 1(1) of Ontario Regulation 419/05 defines the “ASHRAE method of calculation” to mean the method of calculation described in Chapter 46 (Building Air Intake and Exhaust Design) of the 2019 ASHRAE Handbook – HVAC Applications, published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers.
  3. The SCREEN3 dispersion model on the USEPAs website, or available from the MECP.

In addition, section 13 of Ontario Regulation 419/05 provides a list of types of meteorological data, including regional surface and upper air meteorological data for use with AERMOD that must be processed using the AERMET model (meteorological preprocessor for the AERMOD model). The current regulatory model version for AERMET is AERMET meteorological preprocessor version 24142.

Under subsection 177 (6) of the Environmental Protection Act, the adoption of an amendment to a document that has been incorporated by reference (for example, AERMOD/AERMET/ASHRAE), comes into effect once the ministry publishes a notice of the amendment in either The Ontario Gazette or the Environmental Registry under the Environmental Bill of Rights, 1993.

Pre-notification of model updates

In keeping with the pre-notification process of the implementation plan, in April 2027 the ministry will not be adopting updated versions of the AERMOD/AERMET or ASHRAE air dispersion models under Ontario Regulation 419/05. In April 2027 the current regulatory models will remain the same:

  1. AERMOD dispersion model
    • will remain as AERMOD version 24142 (version date May 21, 2024)
  2. AERMET meteorological preprocessor
    • will remain as AERMET version 24142 (version date May 21, 2024)
  3. ASHRAE method of calculation
    • will remain as Chapter 46 (Building Air Intake and Exhaust Design) of the 2019 ASHRAE Handbook – HVAC Applications

The approved dispersion models are available online.

Contact

Additional information may also be obtained from:

Ministry of the Environment, Conservation and Parks
Air Monitoring and Modelling Section
Environmental Monitoring Branch
125 Resources Road, Toronto, ON M9P 3V6