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Evaporative Emissions Leak - Frequently Asked Questions

Why did I receive this advisory notice?

The Department of Environmental Quality (DEQ) operates an emissions inspection program in Northern Virginia, due to the area's nonattainment of Environmental Protection Agency (EPA) air quality standards. As part of that program DEQ utilizes on-road remote sensing technology to screen vehicle emissions. The vehicle emissions data is used to determine if emissions exceed pollutant-specific limits. In addition to identifying vehicles with very high tailpipe exhaust emissions in excess of program standards; these remote sensing devices have the ability to identify vehicles with very high evaporative emissions (i.e. fuel) from sources other than the tailpipe. As indicated in the notice that you received by mail, the referenced vehicle was observed by one or more of these remote sensing devices and identified as having excessive evaporative fuel emissions.

But I don't live in Northern Virginia and my vehicle doesn't require an emissions inspection…

This Advisory Program is not required by law or regulation like the other components of Virginia's emissions inspection program. Therefore, any Virginia-registered vehicle that travels through an on-road remote sensing location and is identified as having high evaporative emissions may receive an advisory notice. Unlike notices of violation issued to emitters of high tailpipe exhaust, requiring them to submit to station-based emissions inspections, this advisory notice does not require the vehicle owner to submit the vehicle for inspection. It is simply advising the vehicle owner that their vehicle may have a significant evaporative emissions leak and recommending the vehicle be examined and repaired.

What is an evaporative emissions leak?

Gasoline fuel is comprised of a variety of hydrocarbons, many of which are light, highly volatile and quickly dissipate into the air when released. These hydrocarbons react to form ground-level ozone in the atmosphere. Evaporative emissions are releases of these volatile hydrocarbons via leaks in fuel-related vehicle components. These evaporative hydrocarbon emissions are separate from the exhaust hydrocarbon emissions released from the tailpipe. When you have an evaporative emissions leak, it means that either liquid or vapor fuel-related hydrocarbons are leaking from your vehicle. There are a number of possible causes for this kind of leak such as a loose or defective fuel cap, a defective fuel control device or a loose, cracked or broken hose. If your vehicle is leaking fuel, your vehicle is emitting excess unburned hydrocarbons into the air, thus adversely affecting air quality in Virginia. A liquid or vapor gasoline leak can also reduce fuel economy and, in some cases, pose a fire hazard.

What is an EVAP system?

Because evaporative emissions adversely affect air quality, the EPA requires Evaporative Emission Control (EVAP) systems on vehicles. These systems are designed to store and dispose of fuel vapors associated with your vehicle's fuel storage system and prevent them from being released into the atmosphere. For more information visit the following websites: and

What do I do now?

First, check your fuel cap to ensure it is not damaged, loose, or missing. Although it is unlikely this would result in high enough evaporative emissions to trigger an advisory notice, it can be a source of excess emissions. A loose or missing gas cap may also cause your "Check Engine" light to illuminate on your dashboard. If your gas cap is present and appears to be in working order, it is recommended that you have your vehicle examined by an automotive repair technician with experience repairing EVAP systems. Take a copy of the advisory notice you received from DEQ with you for the shop to reference. The repair facility may charge you a service fee for the examination and any subsequent repairs that are necessary. If you do not have a repair facility you use regularly, you may visit to see if there is a shop located near you that is listed in our database.

Is it safe to drive with an evaporative emissions leak?

While it may be safe to drive with an evaporative emissions leak, you should have your vehicle examined as soon as possible and repair any confirmed leaks. In addition to producing excess air pollution, a liquid or vapor gasoline leak can adversely affect your vehicle's fuel economy and in some cases may present a fire or safety hazard. For more information visit the following website:

Why does DEQ want to know if I take my vehicle to be examined and if any repairs are made?

Part of DEQ's mission is to protect and enhance public health and the environment by controlling present and future sources of air pollution. DEQ ensures the safety and quality of the air in Virginia by monitoring and analyzing air quality data, regulating sources of air pollution, and working with local, state and federal agencies to plan and implement strategies to protect Virginia's air quality. It is estimated that evaporative emissions account for 20% or more of hydrocarbons emitted into the air in the United States. Hydrocarbons are major contributors to ground level ozone and have been linked to several health issues. The information we receive from you will help DEQ model the impacts of these emissions on human health and the environment. Although this advisory program does not require you to do anything, DEQ greatly appreciates those who choose to have their cars examined and repaired, and is further grateful for those individuals who share this information with the agency.

If you discovered a leak and performed any repairs on your own, DEQ would still appreciate hearing from you via the Evaporative Emissions Repair Form you received with your advisory notice. Your feedback will help us evaluate whether the remote sensing technology we are using is operating as designed and provides valuable information we can use in our program evaluation.

If I choose to return the Evaporative Emissions Repair Form to DEQ, where do I send the form?

A completed form may be returned by either you or your repair technician.

Email: (photo or scanned copy)
Mail: Department of Environmental Quality, 13901 Crown Ct., Woodbridge, VA 22193
Fax: (703) 583-3821
Phone: (703) 583-3800 to provide the information to the DEQ Duty Officer