Since smog was first recognized as a serious problem in 1947, inventors and engineers have proposed innovative ideas to get rid of it.

One was to connect all Los Angeles industries to a massive network of concrete exhaust pipes routed to the mountains where pollution could be released above the inversion layer.

If it works for sewage, it will work for air pollution, thought the engineering firm that pioneered the "air sanitation system" concept.

But the system would have required 89 miles of ductwork and the energy to move the large volumes of air would have been several times beyond what Hoover Dam could supply.

Many other ideas surfaced in the 1950s and 1960s to purify, ventilate or wash the air over Los Angeles.

One was to cut holes in the mountains and install huge exhaust fans to blow smog out of the basin. However, blowing or washing away smog proved to be impractical since it involved a land mass of 1,600 square miles and over 200 million tons of air. The enormous energy requirements made the idea impossible.

One scientist suggested blackening whole sections of the eastern mountains so as to store heat and create thermal currents and westerly winds that would blow smog over the ocean.

Seeding clouds to create rain to "wash the air clean" was one method several experts recommended in the late 1950s. Installing jet engines attached to vertical tubes to propel the smoggy air above the inversion layer also was suggested in 1961.

In 1967, a respected Penn State chemistry professor thought he had a better idea. Instead of spending money on tailpipe pollution controls, why not simply fumigate the urban air each summer smog season with a chemical called diethylhydroxylamine, or DEHA. The professor said that would interrupt smog formation because DEHA scavenges the short-lived free radicals that fuel the airborne chemistry of smog.

The only problem was that the chemical posed an even greater health risk than air pollution.

Although these ideas seem quaint today, they were seriously evaluated at a time when no one knew the cause of air pollution or how to control it.

Many other ideas eventually proved successful at reducing pollution, such as baghouses to control dust from factories, vapor recovery systems with "booted" nozzles at gas stations, catalytic converters on cars and powerplants and reformulated gasoline.

- aqmd -