On September 1, 2021, the Oregon Department of Environmental Quality (DEQ) issued a Short-Term National Ambient Air Quality Standards (NAAQS) Compliance Internal Management Directive that will require more work for new sources—and will ultimately apply these requirements to existing sources. The directive is designed to "ensure that short term (1-hour and 24-hour) NAAQS are not exceeded for new sources . . . and for certain new permitting activities in Oregon."

This directive applies to all new, non-intermittent permitted sources with pending applications on or after June 9, 2021, and will later apply to existing permit holders and sources in the Cleaner Air Oregon program who have not conducted modeling. DEQ is also developing specific guidance for data centers.

Currently, DEQ determines the protectiveness of NAAQS by comparing annual emissions to Significant Emission Rates, which were established in 1980s prior to the establishment of 1-hour NAAQS, and are based on maximum annual averages. If emissions are equal to or greater than the Significant Emissions Rates, then the source has to demonstrate protectiveness through refined computer modeling. However, DEQ has determined that the current process does not ensure compliance with short-term NAAQS because of the long-term averaging.

DEQ will now assess potential NAAQS impact for all new sources applying for either simple or standard Air Containment Discharge Permits (ACDPs). Permittees must demonstrate that short-term NAAQS are not exceeded at the nearest receptors.

The first step is to perform a Single Source Impact Analysis—but some sources, including all new or modified sources that trigger major New Source Review or state New Source Review for any pollutant, will be required to demonstrate compliance by performing air quality modeling and risk assessments. This change reflects DEQ's increased focus on shorter term exposure based on data showing that short-term exposure to fine particulates and hazardous air pollutants can exacerbate asthma symptoms.