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Air Quality Program

Washington's Air Quality Designations

When EPA sets or revises an air quality standard, the federal Clean Air Act requires EPA to designate each area of Washington in one of three ways:

  • Attainment (meeting a standard)
  • Nonattainment (failing to meet a standard)
  • Unclassifiable (not enough information to classify)

Each designation is for a specific air quality standard. An area can be in attainment for one standard and nonattainment or unclassifiable for another.

Design values:

Washington’s air quality monitoring network collects data about certain air pollutants. Based on this monitoring data, the state calculates how much air pollution is in the air. This amount is called the "design value." It is compared to the amount that the air quality standard allows.

EPA specifies how to calculate the design value for each standard. For example, the design value (DV) for the 8-hour ozone standard is equal to the average of the yearly 4th highest daily maximum 8-hour value for the most recent three years:
DVozone = (4th highyear1 + 4th highyear2 + 4th highyear3)/3

Design values are typically used to:

  • determine how an area should be designated,
  • assess progress towards meeting air quality standards, and
  • develop control strategies.

EPA’s Office of Air Quality Planning and Standards computes and publishes design values for nonattainment and maintenance areas every year (visit EPA’s web site).


Based on the design values, the state recommends to EPA one of the three designations for each area of the state. EPA reviews Washington’s recommendations.

Final designations:

The Clean Air Act requires EPA to give Washington 120-days’ notice before making final designations and provide the state with an opportunity to respond. Final designations are signed by the EPA Administrator and published in the Federal Register.

How to get involved

Ecology gives public notice and holds a public hearing when Washington makes a recommendation to EPA about area designations or redesignations.

Learn more about areas currently being designated.

Community consequences of a nonattainment designation

A nonattainment area designation tells a community that its air quality fails to meet federal health-based standards. The designation may cause concern about health effects, the suitability of the community as a place to live and work, and possible economic effects. At the same time, the designation may motivate the community to take the needed actions to bring the area back into attainment.

Air pollution can come from industrial, commercial, residential, and transportation activities. Both businesses and individuals may need to take actions to reduce air pollution.


Existing industrial sources of air pollution in a nonattainment area are required to meet Reasonably Available Control Technology (RACT) requirements. RACT may require additional controls on air pollution emissions.

New major industrial sources and existing industrial sources making major modifications must install strict emission controls. To ensure that total emissions either decrease or have no net increase, a source must also reduce its emissions, or find partners who agree to reduce their emissions elsewhere in the community.


People also contribute to air pollution. Polluting activities include driving, home heating, painting, indoor and outdoor burning, and even lighting fireworks on special occasions.

The motor vehicle Emission Check Program, restrictions on outdoor burning, and burn bans for wood stoves and fireplaces in some areas help reduce pollution. Voluntary efforts to reduce air pollution are also important. These include driving less, burning less and more efficiently, replacing old wood stoves with new, certified stoves or cleaner forms of heat, improving home energy efficiency, and using paints and finishes with low amounts of Volatile Organic Compounds.

What happens after areas are designated

When EPA designates an area nonattainment, Washington normally has three years to develop a plan that will become a part of the overarching Washington’s State Implementation Plan (SIP). For brevity's sake, the new plan is often referred to as SIP and not a SIP revision, thus you can hear about different SIPs, for example PM2.5 SIP or Regional Haze SIP. The new plan outlines the actions the state will take to improve air quality in the area that violates the federal standard. Each SIP or SIP revision must be submitted to EPA for approval after public notice and a public hearing.

Learn more about SIP documents.


EPA has authority to redesignate an area:
  • from nonattainment to attainment if the area meets the standard, or
  • from attainment to nonattainment if the area fails to meet the standard.

The federal Clean Air Act does not allow EPA to redesignate a nonattainment area to unclassifiable.

Washington’s Governor or Ecology’s Director (as the Governor’s designee) can petition EPA to redesignate a nonattainment area to attainment. EPA may approve the redesignation only if all of the following conditions are met:

  1. Air quality monitoring data shows the area meets the standard.
  2. Reductions in the area’s emissions are permanent and enforceable.
  3. The SIP developed for the area meets the requirements of the federal Clean Air Act and receives full approval from EPA.
  4. EPA fully approves a 10-year Maintenance Plan for the area submitted by Ecology as a revision to the SIP.
  5. The area meets requirements of the Clean Air Act for general SIPs and nonattainment areas.

For more information

Contact Us


Washington’s recommended PM2.5 designations:
Letter to EPA 
Response to Comments

Maintenance Areas

State Implementation Plans