Car Emissions: An Overview

Written by: Bonnie Gringer

As a general rule, the exhaust emissions from a single family automobile do not represent a significant accumulation of air pollution, especially when compared to the emissions from the smoke stacks of power plants and factories. However, the concentration of a large number of vehicles in a highly populated area can create an emissions problem that turns into a major environmental and health hazard. The engineering behind a car emission system has changed considerably over the years, but there are still gases being released into the air that should be of concern to the general population. By understanding the harmful emissions that come from auto exhaust, people can take a more active role in reducing the pollution that comes from vehicle traffic.

Types of Auto Emissions

The three types of auto emissions are evaporative emissions, refueling losses, and exhaust emissions. It is interesting to note that the car does not always need to be running to be giving off emissions.

Evaporative Emissions

Gasoline, antifreeze, and other auto liquids are made up of hydrocarbons that can be released into the air in many different ways. Diurnal evaporation is a process where gasoline evaporates from the engine thanks to the rise in the temperature outside. The hotter the day gets, the more emissions vehicles give off. Running loses are fumes given off by the gasoline when the car is running, while hot soak emissions occur after the engine has been turned off but is still warm.

Refueling Losses

Whenever you put fuel in your vehicle, there are emissions that are given off into the atmosphere. If you watch closely as you fuel your vehicle, especially on hot days, you can see the emissions as they leave.

Exhaust Emissions

These are the fumes given off after the engine has burned the gasoline in the course of operating the vehicle. These are the emissions that are most evident and the ones that have been the subject of a variety of changes in laws over the years.

Perfect Versus Typical Engine Combustion

The combustion process in a vehicle engine is actually designed to emit almost no emissions at all. However, the conditions that would allow no emissions exist only in a perfect world and are in stark contrast to the typical engine combustion process.

Perfect Combustion

In a perfect combustion scenario, oxygen in the atmosphere would combine with all of the hydrogen in the gasoline to create almost pure water. The oxygen would then break down the carbon in the gasoline into carbon dioxide (CO2) and leave the nitrogen in the air unaltered.

Typical Combustion

Because of the significant amount of variables involved in the combustion process, it is impossible to get a perfect combustion scenario. The reality is that the gasoline mixes with the atmosphere and produces hazardous emissions made from excess hydrocarbons added to the nitrogen oxides, carbon monoxides (CO), carbon dioxides (CO2), and water.

Types of Exhaust Pollutants

Each of the emissions as the result of typical combustion have their own level of toxicity and, when combined with other elements such as water droplets in the atmosphere, can create hazardous pollution scenarios. Each element of exhaust emissions carries its own properties, which can become significant problems when large groups of vehicles are constantly traveling the same roads day in and day out.

Carbon Dioxide (CO)

When people think of carbon dioxide, they generally feel as though it is not a pollutant. Most people remember carbon dioxide from high school chemistry as a part of the process of creating vital oxygen. But the amount of carbon dioxide being released into the atmosphere has increased dramatically thanks to auto emissions, and it has the potential to trap the energy from the sun and heat the surface of the planet.

Nitrogen Oxides (NOx)

The concept of acid rain is something that is often associated with areas where factories are located. But when the nitrogen and oxygen from auto emissions mix, they create a variety of toxic compounds called nitrogen oxides. As these nitrogen oxides are emitted into the air, they create the situation that allows for toxic acid rain.

Carbon Monoxide (CO)

Carbon monoxide is one of those toxic compounds that is created as a result of the imperfections of the combustion process. This is a compound that can affect a human’s bloodstream and cause complications for people with any kind of heart condition.

Controlling Emissions

The Environmental Protection Agency was given a full range of legal tools to use in the Clean Air Act of 1970 to bring auto emissions under control. The first thing the EPA did was limit the amount of emissions that autos can put into the atmosphere. In response to the EPA’s new rules, the auto industry created several innovations that have significantly cut down on harmful auto emissions. In 1975, the first catalytic converter was installed on vehicles, and it helped to filter out the more toxic emissions. From there, the auto industry has taken many significant steps toward curbing the amount of emissions that autos put into the atmosphere.

The successes that the EPA’s emissions laws created have been overshadowed by the significant increase in the amount of vehicles on the road. While the automakers have managed to cut emissions by as much as 95 percent, the amount of emission pollution continues to be an issue as more and more cars are put on the road every year.