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Air Quality Program

Meeting Clean Air Rule Requirements

Organizations covered by the Clean Air Rule (CAR) are required to reduce their emissions and report their reductions every three years. Emission reduction units (ERUs) provide organizations a way to comply with the rule regardless of whether they can reduce emissions at their facility or not. One emission reduction unit is equal to one metric ton of carbon dioxide equivalent. ERUs need to be verified by an approved third party and reported in the online tracking system.

How an organization can meet their requirements

Organizations can cut emissions by making changes at their facility. They can do this by:

  • installing more efficient equipment,
  • changing their fuel sources, or
  • modifying processes to reduce their carbon pollution.

If an organization reduces their emissions more than required, the extra reductions can become ERUs. Organizations can trade or sell their ERUs to other businesses in the program. Organizations can also save their ERUs for future use. ERUs can be saved up to 10 years.

Organizations can get ERUs from other sources

If an organization does not reduce enough emissions at their facility to meet their requirements, they must get ERUs from another source. They can do this in three ways.

  1. Getting ERUs from other Washington organizations in the CAR Program
    Organizations can buy or trade ERUs with other businesses in the CAR Program. Businesses that are not covered by the rule can voluntarily participate and sell or trade their ERUs as well. Organizations can combine this option with other ways to comply or use it for 100 percent of their compliance.
  2. Sponsoring a program or project
    An organization can get ERUs by sponsoring a program or project. An example of this is a dairy farm building a digester that turns methane from manure into energy. To qualify, programs and projects must reduce emissions in Washington. This option can be combined with other ways to comply or used for 100 percent of compliance. Organizations have three options when it comes to sponsoring programs and projects.
  3. Purchasing allowances from outside of Washington
    Organizations can buy allowances from approved carbon market outside of Washington. An allowance is a unit used in cap and trade carbon emission reduction programs. An allowance can be used to generate one ERU. Allowances must be removed from service in their original programs after being used for the Clean Air Rule. Unlike the other options, the number of allowances an organization can use for a compliance period reduces over time. In order to become an approved program, allowances must be available for purchase and the program’s methods need to be similar to those of Washington’s Greenhouse Gas Reporting Program.

    We are currently determining the carbon markets for the Clean Air Rule. Visit our Clean Air Rule page for more information.

Amount of allowances allowed to be used

Compliance Period


2017 – 2019 100%
2020 – 2022 100%
2023 – 2025 50%
2026 – 2028 25%
2029 – 2031 15%
2032 – 2034 10%
2035 and beyond 5%



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