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New Hampshire Department of Environmental Services

Please Turn Engine Off

An engine that is burning fuel without performing work is idling. Sitting in traffic, picking up or dropping off passengers, warming up your car or engine are all examples of idling. Idling is inefficient because it burns fuel needlessly. In addition, idling puts wear and tear on an engine and contributes to air pollution-related health effects and climate change

Idling is especially significant with diesel-powered trucks, buses and off-road equipment. That is because emission standards have lagged behind gasoline-powered vehicles and they tend to idle more due to the way they are used. School buses are a special concern because the emissions can be harmful to children whose respiratory systems are not fully developed.

Some Idling Facts and Figures

  • Thirty seconds of idling can use more fuel than turning off the engine and restarting it.
  • Idling equals zero miles per gallon. An idling vehicle is the most inefficient vehicle on the road.
  • Idling is not an effective way of warming up engines. The best way to warm up an engine is to drive it.
  • Depending on engine size, one hour of idling can burn a half to a full gallon of fuel. Idling for 10 minutes uses as much fuel as traveling five miles.
  • Every gallon of gas burned produces about 20 pounds of carbon dioxide, a major contributor to climate change.
  • Consuming less fuel by not idling helps to reduce the need to import oil to meet demands. Saving gasoline or diesel represents conservation of a non-renewable natural resource.
  • Breathing exhaust fumes increases the risk of cancer, heart and lung disease, asthma, and allergies, especially in children.

New Hampshire Law Restricts Idling
New Hampshire regulations (Env-A 1100) help to minimize the health and environmental impacts of idling by establishing a limit on the amount of time that engines are permitted to idle. The limit established in the regulations is based on outside temperature, as shown in the following table.

Ambient Temperature Maximum Idling Time Limit

Above 32º F

5 minutes

Between –10º and 32º F

15 minutes

Below –10º F

no limit

Exemptions to these rules are vehicles in traffic, emergency vehicles, vehicles providing power take-off (PTO) for refrigeration or lift gate pumps, and vehicles supplying heat or air conditioning for passenger comfort during transportation.

Anti-Idling Initiatives
Drivers of heavy duty diesel vehicles can have a significant impact on public health and the environment by limiting engine idling time whenever possible. The American Trucking Association (ATA) reports that engine idling not associated with normal driving makes up as much as 30 percent to 50 percent of truck operating hours. Diesel vehicle fleets and drivers can help improve air quality and public health by complying with the regulations and by proactively adopting and promoting policies to further minimize engine idling.

Idling time can be significantly reduced through the use of anti-idling devices, which include direct-fired burners for cab and engine block heating; thermal storage devices for heating and cooling; and auxiliary power units for heating, cooling, and electrical power. These units use only 10 percent to 15 percent of the fuel a diesel truck engine uses and also emit much less air pollution per gallon burned. Information of idle reduction technology can be found under the Hot Topics section of the Idle Reduction webpage

School Bus Anti-Idling Initiative
Air pollution from diesel vehicles has health implications for everyone, but children are more susceptible to this pollution because their respiratory systems are not fully developed. Diesel exhaust typically contains particulate matter (PM), hydrocarbons (HC), and carbon monoxide (CO). Exposure to fine particles in school bus exhaust can result in increased frequency of childhood diseases, such as asthma. At school yards, idling school buses release emissions directly into the breathing zone of children. As children line up to board an idling bus, they are exposed to the vehicle’s emissions at the most concentrated levels. Limiting the amount of idling time not only reduces exposure of school students to the harmful pollutants in diesel exhaust, but it also improves air quality.

In 2002, NHDES teamed up with the New Hampshire School Transportation Association (NHSTA) to launch a voluntary initiative to protect school children and bus drivers from excessive exposure to exhaust emissions from school buses. As part of the initiative, fleet managers and school bus drivers throughout New Hampshire adopted policies and practices to reduce school bus engine idling time whenever possible. For more information about this initiative, visit the School Bus Anti-Idling web page. In addition, New Hampshire recently passed a law that directs school districts to develop a policy for governing air quality in schools, calling on the school boards to “… address methods of minimizing or eliminating emissions from buses, cars, delivery vehicles, maintenance vehicles, and other motorized vehicles used for transportation on school property taking into account the state anti-idling and clean air zone policies established by the Department of Environmental Services.” RSA 200:48 Air Quality in Schools.

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

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