Air Quality Board

Ada County Emission Testing

Senate Bill 1254 – Effect on Emission Testing in Ada County

On March 22, 2022, Governor Little signed Senate Bill 1254, which repeals the emission testing requirement in Idaho Code Section 39-116B. Per the text of the bill, the action becomes effective July 1, 2023.


Currently, the Ada County emission testing program remains in place and vehicle owners are required to test. AQB will continue to send notices to vehicle owners to remind them of the test requirement. Non-compliance with the testing requirement by the deadline date will result in vehicle registration revocation.


As the text of the bill explains, Ada County’s emission testing program began in 1984, due to violations of the carbon monoxide (CO) ambient air quality standard. The program is implemented under local ordinances through the Air Quality Board, as a control measure in the CO state implementation plan (SIP) to reduce pollution. The SIP was approved by EPA and is currently federally enforceable.


The Department of Environment Quality (DEQ) submitted a SIP revision to EPA at the end of 2022 showing that ending emission testing will not affect our area’s ability to maintain compliance with the national ambient air quality standards. If EPA approves that plan, the federal requirement for emission testing will be removed. Local jurisdictions in Ada County would then decide whether to continue to require emission testing under the existing local ordinances, or repeal those ordinances and end their emission testing requirements.

Emission testing is required in Ada County at least through June 30, 2023, and may continue beyond that date, depending on the federal and local actions described above.


Please see the FAQ for additional information: S1254 FAQ 

Emission Testing

Vehicles are one of the largest contributors to harmful air pollution that leads to adverse health effects.  A vehicle inspection program is a proven, cost-effective way to reduce air pollution and maintain good air quality.  Ada County Air Quality Board was created in 1984.  Every year, Department of Environmental Quality reviews the effectiveness of emission testing programs by looking at the annual testing results and using the latest emissions modeling. The emission reductions are compared to the initial modeling reductions that were estimated in 2008 when Idaho Code §39-116B was enacted.  Each year, the program has seen a reduction in ozone precursors (volatile organic compounds and nitrogen oxides).  With each annual review demonstrating greater emission reductions than estimated in 2008, the vehicle inspection program continues to be an effective control measure to minimizing harmful pollutants.



First Notice for Website Dec_21.pdf
Overdue Notice for Website Dec_21.pdf

Air Quality

Maintaining Idaho’s air quality is a job where everyone can play a role. Poor air quality is unhealthy for everyone, but especially for children, senior citizens and people with respiratory conditions like asthma. With cleaner air, there are fewer trips to the emergency room and lower respiratory illness rates. It also keeps wildlife and plant life thriving.

Cleaner, healthier air requires both local and regional efforts. The Air Quality Board (AQB) leads Idaho in caring for the state’s air quality by partnering with communities, business and industry, organizations and private citizens to provide the knowledge and tools necessary to create workable solutions to air quality issues. 

Air Quality Index

After the amount of pollution is measured, it is compared to the federal standard. To make it easy to compare the various pollutants and determine the air quality, the US Environmental Protection Agency (EPA) developed the Air Quality Index (AQI), a guide for reporting daily air quality.

The AQI indicates how clean or polluted the air is in a particular area and identifies potential health impacts. The AQI focuses on health effects that can happen within a few hours or days after breathing polluted air.  Department of Environmental Quality uses the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.

You can think of the AQI as a measuring stick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health danger. For example, an AQI value of 50 represents good air quality and little potential to affect public health, while an AQI value over 300 represents hazardous air quality with potentially serious health impacts.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. So, AQI values below 100 are considered healthful. When AQI values are above 100, air quality is considered to be unhealthy—at first for certain sensitive groups of people, then for everyone as AQI values get higher.

Based on the measurements, air quality is then categorized according to health risk ranging from good to hazardous, with four stages in between. Each stage is assigned a color. Because the AQI is a national index, the values and colors used to show local air quality and the associated level of health concern are the same everywhere in the United States.

To learn more about Air Quality, below are links to the Environmental Protection Agency web sites.