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Vehicle Emissions

Vehicles are one of the largest contributors to air pollution nationwide. Vehicles directly emit many different pollutants including fine particulate matter, carbon monoxide, nitrogen oxides, sulfur oxides, and volatile organic compounds. These pollutants can combine in the air to form PM2.5 and ozone, which are the main pollutants of concern in Idaho. These pollutants can lead to serious health conditions such as asthma and respiratory illnesses and can also impact visibility, affect water resources, and damage buildings.

While emissions from a single vehicle may be minimal compared to an industrial source, emissions from many vehicles can have serious impacts on air quality. An Inspection and Maintenance (I/M) program can reduce vehicle emissions and improve air quality by requiring vehicle owners to maintain and if necessary repair their vehicles to obtain compliance with the program.

Idaho Code § 39-116B requires vehicle emissions testing in areas of the state where the monitoring design value exceeds 85% of any National Ambient Air Quality Standard (NAAQS) and where motor vehicle emissions constitute one of the top two pollution sources. 

Idaho has emissions testing programs in Ada and Canyon Counties. In both areas, the design value for ozone exceeds 85% of the NAAQS, and vehicle emissions constitute one of the top two emission sources.

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Ada County has operated its vehicle emissions testing program since 1984, covering all cities and unincorporated parts of the county except Kuna. This program is managed by the Air Quality Board and follows the requirements in local ordinances. For questions about inspection station locations, program rules, vehicle testing, exempt vehicles, or waiver requirements, call the Air Quality Board or visit the Air Quality Board website.

Air Quality Board
700 NE 2nd Street, Suite 200
Meridian, ID 83642
(208) 377-9191

In 2010, vehicle emissions testing started in Canyon County and the city of Kuna (located in Ada County).

The Canyon County program, which includes the city of Kuna, is managed by DEQ and its contractor, Applus Technologies Inc. This program follows the requirements in the Rules for the Control of Air Pollution in Idaho IDAPA If you have questions about inspection station locations, vehicles subject to testing, exempt vehicles, or waiver requirements, call Applus Technologies or visit the Canyon County Program website.

Applus Technologies Inc.
2216 Cortland Place
Nampa, ID 83687
(208) 461-1232

Contact the Vehicle Inspection & Maintainance Coordinator at our Boise Regional Office.  

DEQ evaluates the emissions testing programs annually. This task includes estimating emission reductions attributable to the programs and evaluating their effectiveness.

Results show that lowering motor vehicle NOx and VOC emissions reduces ozone in the Treasure Valley. These emission reductions are comparable to those estimated when Idaho Code § 39-116B was enacted. Read the most 2020 Treasure Valley Vehicle Inspection and Maintenance Programs report.

Consider the many ways you can reduce the pollutants emitted from your car.

Maintain your vehicle.

  • Repair your vehicle when the check engine light is on. The check engine light indicates that your vehicle has a problem that could decrease its efficiency and increase the pollution it emits.
  • Get regular tune-ups. Vehicles with worn spark plugs, clogged fuel, or air filters do not run efficiently and emit more pollution.
  • Keep tires properly inflated and wheels aligned to reduce tire drag on the road. Gas mileage drops 1% for every pound below the recommended pressure level.
  • Do not top off the gas tank. This allows harmful chemicals to be released into the air.

Drive less.

  • Ride the bus, carpool, walk, or bike to reduce the number of cars on the road.
  • Organize a carpool at work. Call 208-345-POOL for help.
  • Combine trips to the same areas. Once you arrive, park your car, and walk between destinations.

Drive wisely.

  • Avoid carrying extra items. Each additional 100 pounds increases the amount of gas used by 4%.
  • Place items inside the vehicle instead of on the roof racks and remove roof racks when not in use. The drag from a rack increases gas consumption by almost one mile per gallon.
  • Drive at a steady speed and avoid stop-and-go traffic.
  • Use the air conditioner only when necessary. Air conditioners can reduce your gas mileage by 20%.
  • Avoid idling. Restarting a warm engine takes less fuel than running for 30 seconds.
  • During hot summer, fuel vehicles in the evening to reduce the release of volatile organic compounds that contribute to ozone formation.
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