&EPA
United States
Environmental Protection
Agency-

Office of Air and Radiation
6401

April 1997
;EPA #420-F-97-004a
                                                       The Drive to
                                                                                 An Introduction
                                                                                 to Enhanced Vehicle
Emission Testing

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About  the Emission Testing Law
In 1990, Congress amended the Clean Air
Act to require states to Implement vehicle
inspection and maintenance (I/M) pro-
grams. Highly populated areas that fail to
meet air quality standards must implement
either a "basic" or "enhanced" I/M pro-
gram, depending on the level of pollution.
The Act also requires additional controls
on stationary sources (i.e., power plants)
of air pollution, so everyone contributes to
solving this important national problem.
      uying a car or truck is one of the biggest
      investments you make. To protect that
      investment, you must keep your vehicle in
 good working order. An important way to do that
 is to have your vehicle's exhaust emissions tested.
 Besides reducing air pollution, emission testing can
 help improve fuel economy and extend the life of
 your vehicle.
 Emissions and Your Vehicle
- High emission levels do more than pollute the air.
 They are symptoms of poor engine performance,
 which can cause decreased fuel efficiency and may
 signal possible engine troubles down the road.
 You can extend the life of your vehicle by following
 the manufacturers maintenance recommendations.
 Regular maintenance generally can help prevent
 many emission problems from developing.
 If emission problems do occur, studies show that you
 can improve your vehicles fuel efficiency by an aver-
 age of 6% to 13% by having die'problem repaired.
 This could mean a savings of $40 to $90 per vehicle
 every year.
 In addition to lowering fuel costs and increasing
 your engines efficiency, high-tech test-only emission
 testing is the most effective, least expensive way to
 identify polluting vehicles, which are die largest
 single source of air pollution in the United States.

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 Emissions and the Environment
 " How Do Emission Tests "Work?
*- By identifying vehicles that pollute, emission testing
  helps reduce risks to our health and the environment.
  It specifically works to reduce emissions of two major
  pollutants — carbon monoxide and ozone.
  > Carbon monoxide (CO) is the deadliest com-
    ponent of air pollution. It is a colorless, odorless gas
    that results from incomplete combustion of fuel.
    CO goes direcdy from a vehicles tailpipe into the air
    we breathe.  It enters the bloodstream through the
    lungs and forms a compound that inhibits the bloods
    capacity to carry oxygen to die brain and tissues.
    This poisonous gas affects the elderly, infants,
    people with heart and respiratory disease, and
    even healthy individuals when they exercise.
    Acute exposure to CO can cause brain damage.
    Motor vehicles typically contribute 90% of the
    carbon monoxide pollution in urban areas.
 >" Another toxic component of air pollution is
    ozone, formed when hydrocarbons (HCs)  and
    oxides of nitrogen (NOx) combine with sunlight.
    Both HCs and NOx are emitted from vehicles.
    In die upper atmosphere, ozone benefits life by filter-
    ing out ultraviolet radiation from die sun. At ground
    level, however, ozone can be damaging to plants, ani-
    mals, and human tissue. Ozone is also a severe irri-
    tant that causes the choking, coughing, and stinging
   eyes associated with smog. High ozone concentra-
   tions can present serious problems for children, the
   elderly, and diose with existing lung conditions.
   In typical urban areas, as much as one-half or
   more of these pollutants come from cars,  trucks
   and buses.
"**" Emission tests check the gases your exhaust system
   releases and diagnose how well the entire system- is
   working. They compare your actual emissions to
   die allowable standards for your vehicle model year
   and type.
   There are two types of inspection and maintenance
   (I/M) testing programs — basic and enhanced.
   Which test is required for your vehicle depends on
   die level of air pollution in your area. Since most
   motorists are familiar with basic I/M programs
   begun in the 1980s, this brochure focuses on
   enhanced I/M.
   Enhanced I/M refers to performance-based
   emission control initiatives selected by each state to
   meet enhanced performance standards in reducing
   air pollution locally.
   There are several advanced technologies which can be
   used to evaluate overall engine performance. These
   high-tech, mass-based transient tests are currendy
   used in areas where pollution is more severe. The tests
   are very effective because they simulate actual driving
   conditions (including idling, acceleration, various
   speeds, and load levels) allowing emissions to be calcu-
   lated more realistically.  In addition, the sophistication
   of this technology reduces or eliminates false passes
   and false failures common in I/M testing.
   A trained inspector, experienced in testing proce-
   dures and proper handling of vehicles, drives the
   vehicle onto a dynamometer (a vehicle treadmill)
   and performs some or all of the following tests:
   >• An exhaust test accurately measures, under
     real-world driving conditions, the amount of pol-

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   lutants coming through a vehicles tailpipe and
   compares that amount to the allowable standards.
   In general, tests take anywhere from 30 seconds to
   four minutes, or about two minutes.
>• A purge test determines whether the gasoline
   vapors are properly captured from the fuel tank
   and charcoal canister and routed to the engine
   where they are burned as fuel. This is essential for
   pollution control and good fuel economy. This
   test is performed during die exhaust test.
>• A pressure test checks the vehicles evaporative
   emission control system for a proper seal.
X An on-board diagnostic (OBD) test.
   Engine and emission control systems on todays
  vehicles are controlled by on-board computers.
   OBD computers monitor these systems and store
  codes when a problem is found so inspection or
   repair technicians can access these codes.  The
  OBD test checks a log for any emission control
  problems recorded by the computer.
>-A visual check of major emission control
  components.
In addition to IM240, there are other tests, inspec-
tions, and measures that states may select in develop-
ing their programs to fit their local needs.

      By identifying vehicles that pollute,
   emission testing helps reduce risks to our
  health and the environment. It specifically
   works to reduce emissions of two major
  pollutants — carbon monoxide and ozone.
                                                              The Future of Emission Testing
- Only by testing can we be sure that a vehicle's
 emission control system is working properly.
 Today's tests are geared toward identifying emission
 control issues and having them repaired. Emission
 tests and other visual inspections rely on sophisticat-
 ed computer technology both at the testing site to
 recognize if and how the car contributes to the
 pollution problem and at the repair facility where
 diagnostic equipment helps die technician isolate
 the cause so that it can be eliminated.
 New technology, however, promises to make testing
 even easier. For instance, all new cars and trucks are
 equipped with OBD computers that monitor all die
 systems in a vehicle. OBD checks, if found to be
 effective, may replace other kinds of tests in the future.
 Advanced technology in modern vehicles can gready
 improve the quality of our air, but only if the engine
 is functioning properly. As vehicle owners take
 personal responsibility to maintain their vehicles and
 verify their engine performance through emission
 testing, America's #1 source of air pollution will be
 put in check.
 A well-maintained car will last longer, cost less to
 operate, and be part of the solution to healthier,
 cleaner air.

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