Emissions testing may seem like an inconvenience, but it grew out of a response to a series of public health crises in the mid-20th century. Before the regulation of vehicle exhaust, the resulting air pollution regularly killed scores of Americans every year and injured thousands more.
With the development of emissions testing standards, the impact of industrial and vehicle emissions on human health was substantially mitigated. Today, we'll explore the history of vehicle emissions testing in America and help you prepare your car to pass.
Why Emissions Testing?
In the middle of the 20th century, air pollution in cities and industrial areas had a noticeably impact on quality of life across America. In major metropolitan areas, photochemical smog was becoming a direct threat to human health as early as the late 40s.
In Europe, especially London, smog was identified as an issue much earlier; the first attempt to control air pollution through the regulation of coal fires within London city limits took place at the order of King Edward I in 1306. These initial efforts – like those of Queen Elizabeth, 250 years later – were mostly ineffective, despite carrying a penalty of death for violation of the royal edict.
One of the earliest recorded public health disasters in America due to uncontrolled emissions occurred in October of 1948, in the town of Donora, Pennsylvania. A temperature inversion trapped air pollution from two nearby US Steel Plants – the Donora Zinc Works and the American Steel and Wire plant – creating a ground-level pocket of fluorine, nitrogen dioxide, and sulfuric acid smog over the town. This lasted for four days, from October 27th - 31st. By the time a passing storm broke the inversion pattern, twenty residents were dead and approximately 7,000 seriously ill.
The next few years brought several similar incidents and an emerging scientific understanding of the nature and origin of smog. When airborne pollutants, especially volatile organic compounds and nitrogen oxides, interact with sunlight in the atmosphere, they break down and change into a number of harmful compounds and chemicals. The resulting chemical soup can reach dangerous levels at ground height when a layer of warm air traps colder air at the surface – known as a “temperature inversion”. These conditions concentrate pollutants at ground level, preventing dispersal and increasing human exposure to immediately threatening levels.
After determining vehicle exhaust to be the largest contribut0r to dangerous atmospheric pollution, the state of California moved in 1966 to set emissions control standards via the California Air Resources Board (CARB). This was the second major step the state took to bring auto emissions under control; previously, California (and, later, New York) had mandated the installation of positive crankcase ventilation systems in all newly purchased cars from 1961 onwards. These systems redirected unburnt hydrocarbons from the exhaust stream back into the intake, so they could be burned rather than released into the atmosphere. Following promising reductions in air pollution, the CARB and the newly-formed EPA began to gradually tighten emissions standards in the coming years.
The automotive industries have kept pace with evolving air quality legislation through technological refinements such as the catalytic converter and the removal of lead from gasoline. (As an interesting knock-on effect of emissions regulation, the effective end of lead pollution from vehicles may be responsible for the marked decrease in violent crime over the past twenty years.)