Rules on air quality and pollution
The rules you need to follow if your business emits contaminants to air and how to comply with the local air quality regulation.
Important notice
At this time, the ministry strongly encourages email submissions for site-specific standards and technical standard registrations. Submission should be sent to the Client Services and Permissions Branch by email at enviropermissions@ontario.ca.
If you have any questions, please contact the Client Services and Permissions Branch by email, or by phone at
The law
Ontario regulates contaminants released to air by various sources, including local industrial and commercial facilities, to limit exposure to substances that can affect human health and the environment.
If your business emits any contaminants to the air, you must comply with the regulation by meeting certain standards that may apply.
There are three compliance approaches under the regulation:
- meet the general air standard
- request and meet a site-specific standard
- register and meet the requirements under a sector-based technical standard (if available)
Source law
You can find a complete set of rules related to this activity in:
General air standards
Air standards are legal limits for contaminants in air.
Air standards are used to assess the contributions of a contaminant to air by a regulated facility. Under this approach, compliance is assessed by comparing the estimated maximum point of impingement (POI) concentration resulting from a facility’s emission to the air standard.
If a facility can demonstrate that the maximum concentration of the contaminant emitted by the facility does not exceed the air standard, no additional requirements are triggered under the regulation. Most facilities in Ontario meet the general air standards.
New or updated standards are phased-in to allow industry the time needed to comply with the regulation. More advanced air dispersion models are also phased-in by sector.
You may also need to have an Environmental Compliance Approval.
Learn more: Environmental Compliance Approval
Request a site-specific standard
If your facility faces challenges in meeting a required air standard, you may be eligible to submit a request for a site-specific standard. This is an air concentration approved by a Ministry of the Environment, Conservation and Parks director for an individual facility.
To make a request for a site-specific standard, you need to set up a pre-submission consultation meeting with the ministry’s Standards Development Branch.
To set up a consultation, you must submit the following original documents to the ministry and a copy to the branch:
- request form
- Emission Summary and Dispersion Modelling Report
- including the results from a modelling/monitoring study
- an assessment of the magnitude and frequency of exceedance of the standard
- technology benchmarking report – assessing and ranking technical methods for reductions in the contaminant concentrations and providing an assessment of feasible technologies
- economic feasibility analysis (optional)
- public consultation report – summarizing the results of mandatory public meetings with the local community
- action plan with a schedule of dates/timelines
The request can be approved for a period of at least five years and not more than 10 years, to ensure continual improvement and the re-evaluation of technical or economic considerations.
Guide to Requesting a Site-Specific Standard
Download request for approval form
Public meeting
If you are requesting a site-specific standard, you must:
- host a public meeting and inform local stakeholders and the ministry at least 15 days before the meeting
- publish a notice of the meeting in a newspaper with a general circulation in the area
- make your supporting documents available to the public before submitting your application
- organize a community forum where you:
- respond to questions
- provide a plain language information package that includes an outline of your proposed action plan
- offer to provide a complete written copy of the proposed package to request a site-specific standard
- provide a written summary of the public meeting and submit that as part of your request
Environmental Registry
Your request for a site-specific standard will be posted on the Environmental Registry for a minimum of 45 days.
The ministry will consider all comments received in making a final decision on the approval for a site-specific standard.
Renewing a site-specific standard
You may request a renewal of your approval for a site-specific standard.
Renewal requests must include:
- an application form
- an updated technical and/or economic reports
If significant changes are proposed public meetings will also be required.
Download renewal application form
Register for a technical standard
A technical standard is a technology-based solution designed for two or more facilities in a sector that may not be able to meet an air standard for technical or economic reasons.
There are two types of technical standard:
- industry standard – based on an industry sector (e.g., foundries)
- equipment standard – for a source of emissions from one or more sectors
A technical standard may be developed:
- at the request of industry
- if the ministry identifies certain sectors that may be better controlled, monitored or managed by the technical standard compliance approach
A technical standard specifies:
- the steps to be taken to address the key sources of a contaminant
- timeframes for implementation
If the technical standards available address all sources of that contaminant from your facility, then your registered facility will be exempt from the air standard but must meet the requirements of the technical standard.
When facilities in a sector operating under a technical standard cannot meet one or more general air standards, the focus is on managing the emissions that contribute most to local exposures.
Technical standards are currently available for sectors described in the publication Technical Standards to Manage Air Pollution.
Some facilities registering under a technical standard may be required to do public outreach, which may include hosting a public meeting or providing other information to engage the local community in their plans.
Notifications of exceedances
You must notify your local Ministry of the Environment, Conservation and Parks District Office if emissions from a facility exceed any:
- air standard
- guideline (or may be causing an adverse effect)
- upper risk threshold
You must:
- submit an abatement plan within 30 days of notification for emissions that exceed an air standard, guideline, or may cause an adverse effect
- submit an Emissions Summary Dispersion Report within three months of potentially exceeding an upper risk threshold
Contact your local Ministry of the Environment, Conservation and Parks Office
Download and complete notification of exceedence form
Reporting
If you operate a facility listed in a sector in Schedule 4 or Schedule 5 of the regulation, you need to assess your air emissions every year by preparing an Emission Summary and Dispersion Modelling report.
The report:
- summarizes all the air emissions from your facility
- uses air dispersion models or a combination of dispersion models and air monitoring data to assess whether air standards/guidelines are met
Reports must be:
- accurate as of December 31 in the year the report was prepared
- updates must be completed no later than March 31 in the following year
Facilities are also required to develop an Emission Summary and Dispersion Modelling report if:
- applying for an Environmental Compliance Approval
- applying for a site-specific standard
- exceeding an Upper Risk Threshold
- requested by the ministry through a notice
You must:
- make the report available at the facility being reported on
- post the executive summary on your public website or make it available during regular business hours at the facility being reported on
- make the report available to ministry staff when they perform inspections or audits of your facility
See: schedule 4 or 5 for a list of facilities
Apply for an Environmental Compliance Approval
Air dispersion modelling
An air dispersion model is a mathematical tool used to assess point of impingement concentrations that are then compared to ministry air standards and guidelines.
A point of impingement is the point at which a contaminant contacts the ground or a building.
Facilities can use these approved dispersion models:
- US EPA dispersion models: AERMET and AERMOD (version 22112) and SCREEN3 (for US EPA guidance on AERMOD visit SCRAM website)
- Chapter 46 (Building Air Intake and Exhaust Design) of the 2019 ASHRAE Handbook – HVAC Applications: this method of calculation for Building Air Intake and Exhaust Design is copyrighted - a license must be purchased from the American Society of Heating, Refrigerating and Air-Conditioning Engineers
Facilities need to get ministry approval before using other dispersion models or other model versions, including more recent AERMET and AERMOD versions (e.g., version 23132) (see below on the latest updates to Ontario’s air dispersion models).
We do not provide any model development related support or licensing for these models.
Latest updates to Ontario’s air dispersion models
The Ministry has not adopted updated versions of the AERMOD/AERMET or ASHRAE air dispersion models in April 2024, under Ontario Regulation 419/05 Air Pollution - Local Air Quality Regulation (O. Reg. 419/05).
Accordingly, the approved versions of these models under O. Reg. 419/05 adopted on April 13, 2023, remain unchanged. This means that AERMOD version 22112 is still the regulatory version of the model and facilities/proponents should continue using that version for any regulatory air dispersion modelling under O. Reg. 419/05. It also means that proponents/facilities can not use more recent US EPA versions without facility specific Ministry approval under s7(1) of O. Reg. 419/05. If proponents/facilities need more information on the models that were updated on April 13th, 2023, please refer to ERO Number 019-6897.
As per the ministry’s Model Update Implementation Plan, the next potential regulatory model version update would not occur before April 2025, with pre-notification of an impending update to occur in October 2024.
Air dispersion modelling resources and guides
Guideline A-11: Air Dispersion Modelling Guideline for Ontario
Technical Bulletin on Flare Modelling
Request for use of site specific meteorological data
Request for use of a specified dispersion model
Regional Meteorological and Terrain Data for Air Dispersion Modelling
Reporting resources and guides
Guideline A-10: Procedure for Preparing an Emission Summary and Dispersion Modelling (ESDM) Report
Combined Assessment Of Modelled And Monitored Results (CAMM) as an Emission Rate Refinement Tool
Request for approval of a plan for combined analysis of modelled and monitoring results
Site-specific standards forms and guides
Guideline A-12: Guideline for the Implementation of Air Standards in Ontario
Guide to Requesting a Site-Specific Standard
Request for approval for a site-specific standard
Application of Cost Effectiveness Indicators - Section 32 Requests
User Guide: Application of Cost Effectiveness Methodology - Section 32 Requests
Technical standards forms and guides
Guide to Applying for Registration to the Technical Standards Registry - Air Pollution
Application form to register to the technical standards registry
Industry standard supplemental application form - foundries
Industry standard supplemental application form – forest products
Industry standard supplemental application form – pulp and paper