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Auto Emissions in the U.S.

Setting the standard

While the emissions released from a single car in the United States may seem insignificant compared to those of, say, a chemical processing plant, vehicles are, in fact, the single greatest polluter in cities across the country. As we know, the power to make a car go comes from the energy released when an engine burns fuel. The byproducts of this process of combustion are exhaust emissions that form ground-level ozone, a major component of smog that, according to the Environmental Protection Agency (EPA) is, "our most widespread and intractable urban air pollution problem." Ozone can also cause eye and throat irritations and damage lungs and aggravate respiratory illnesses. Vehicle exhaust also contributes to the formation of acid rain, can reduce the flow of oxygen in the bloodstream (which is especially dangerous for people with heart disease), and can increase the effects of global warming.

Improvements

It is important to note that today's vehicles have a vastly improved ability to regulate and minimize tailpipe emissions and the quality of gasoline formulations has also contributed greatly to lowering exhaust emissions. Since the late 1970s and early '80s, the EPA, both at a state and federal level, has implemented guidelines for automobile emissions that have contributed to significantly lowered emissions levels for automobiles, though evaporative losses, which are as destructive and pollutant, now account for the majority of hydrocarbon pollution (from newer model cars on hot days, for example).

Hot Soak

Evaporative emissions occur when, for example, on hot days gasoline heats up and evaporates from both the gasoline tank and wherever fuel may be throughout the engine. They are also released from a hot engine and exhaust system when the car is running and/or idling. After the car is turned off, the engine still remains hot for a period of time, and gas vaporizes then, as well, even when the car is parked. This is called "hot soak." Vapors are also released when refueling: your gas tank always has gas vapors in it, and as new fuel is pumped in, the vapors are pushed out. All of this contributes to the air quality where we live.

Testing

To ensure that a vehicle is within those limits (which are based on model year), periodic testing is required. Often referred to as an I/M Program (Inspection/Maintenance), this testing is mandated by the EPA. In addition, individual states have programs that work within or in addition to the EPA standards, which have gotten progressively tougher since the original Clean Air Act of 1970.

Changes

As noted above, to improve air quality throughout the country, the EPA sets standards for emissions. Beginning in 1970 and continuing through the Clean Air Act of 1990, the EPA regulates automobile pollution through various laws meant for both automobile manufacturers and the car-owning public. Automakers have developed more efficient engines, charcoal canisters, catalytic converters, and, more recently, more sophisticated computerized equipment to optimize the efficiency of the catalytic converter. Combined with regular maintenance and cleaner-burning fuels, these advancements help to control automobile emissions.

Canisters

Developed after the 1970 Clean Air Act, the charcoal canister works to "collect" the hydrocarbon vapors, which are the result of fuel molecules in the engine that either burn partially or do not burn at all. Through a chemical reaction between nitrogen oxides in the air and sunlight, ground-level ozone (a major ingredient in smog) is formed. Ozone is a highly toxic, carcinogenic chemical compound. By collecting the hydrocarbon vapors, the charcoal canister works to reduce nitrogen oxides.

Converters

The catalytic converter, debuted in 1975, significantly reduces hydrocarbon and carbon monoxide emissions. Located in the exhaust system, the catalytic converter resembles a muffler, as they both have stainless steel outer shells, although they are quite different in substance and function. The catalyst, which is anything that induces or accelerates a change or reaction, is made from a noble metal like palladium or platinum. The converter uses fuel and oxygen to stimulate its internal catalyst, which then consumes the poisonous gases like carbon monoxide, hydrocarbons, and nitrogen oxides. While the catalytic converter cannot eliminate these emissions completely, it greatly reduces them by changing these vapors to harmless carbon dioxide, nitrogen, oxygen, and water.

While the catalytic converter does not need any special maintenance of its own, proper engine care and maintenance is essential. If you notice smoke from the tailpipe, hesitation, bucking, or poor performance from your engine, you must get it looked at. If you damage your catalytic converter it may need expensive work or replacement; will likely increase engine temperatures, and will probably cause you to fail an emissions test. Remember: take care of your engine, and your engine will take care of you.

Diagnostics

Since the 1990 Clean Air Act, manufacturers have been required to equip cars with computerized diagnostic systems that can immediately identify malfunctions that effect vehicle emissions. Although they've been around for several decades, since 1996, when the second generation of onboard diagnostics (OBDII) systems were developed, these computers have greatly raised the efficiency of engine performance. Gathering information like the manifold air temperature, coolant temperature, throttle position, and various pressure and oxygen sensors, the diagnostic system is able to gather information to deliver to the car's powertrain control module, compare values, and issue commands in order to improve and maintain proper engine function as well as reduce emissions.

As with all of the devices pertaining to your vehicle's performance and emissions, properly maintaining the engine, converter, and periodically checking the air pump are necessary for proper maintenance of this system. Any time the "Check Engine" or "Engine Service" lights are triggered, make sure that you do, as a problem ignored now may become larger and vastly more expensive later. As that automotive sage from television once said: "you can pay me now, or you can pay me later."