ir pollution criteria. Another goal of this act was to research the cost -effectiveness relation of available engineering control techniques. Later, during the 70's National Air Quality Standards were set for the major pollutants. Primary standards were set for health, with secondary standards for vegetation and general environmental welfare. Penalties as high as $25.000 per day and a year in prison were authorized for industries that failed to meet the regulations. Automobiles emission standards were set. Additional adjustments to the 70's regulation came along in 1990. Each revised some of the older regulations. Some of which proved to be very strict and unattainable. Overall each new version strengthened and broadened the previous version. Change of Fuels The most direct method of pollution control involves changing the fuel. High sulfur coal was responsible for the greatest smog outbreaks of the early twentieth century. Sulfur oxides and particulates reached dangerous levels in many areas, especially in industrial areas. During the 1960s and 1970s a switch to low sulfur oil, natural gas and nuclear power brought the levels of that kind of smog down to relatively low concentrations. Although complex control devices are available, the fuel switch in power plants accounts for most of the improvement. Of course change can introduce new problems. Natural gas combustion can increase the levels of nitrogen oxides, and nuclear power leads to new problems. Although we know that changing the fuel is not going to stop air pollution, but only reduce it, we are trying to find substitutes which will result to higher efficiency with lower emissions. Smokestack emissions control Particles come in assorted sizes and shapes, and a number of control systems have been designed for removing them from the stream of gases that go up the smokestack. The type of device depends on the type of particle and size. Soluble particles can be drained out of an effl...
