Today, people use compressed air to power tools, as brakes for high speed trains, and to fill car tires. The earliest applications of compressed air were likely early humans using compression in their own lungs to shoot blow darts and stoke fires. However, recent studies show the limitations of compressed air in certain industries.
For centuries, compressed air was used almost exclusively for metal work and mining. Thousands of years ago, ancient Egyptian and Sumerian metal workers used hand-operated and foot-operated bellows to stoke their furnaces. As mining technology advanced in early modern Europe, compressors pumped air below ground to ventilate underground mines. Around 1800, scientists and engineers experimented with using compressed air as an energy source. Early tools like the pneumatic rock drill showed the potential of compressed air to power tools.
Even before the invention of automobiles, tires were filled with compressed air. By the mid-1800s, air-filled tires began to compete against solid rubber tires. The compressed air helped absorb shock, but their durability remained a problem until later that century, when they became popular as bicycle tires. By 1900, the first automobiles used tires filled with compressed air, which soon dominated the market.
As tires evolved over the twentieth century, from bias-ply tires to steel-belted radial tires, the interior of the tire remained the same, filled with compressed air. But while compressed air continued to work well for powering tools, engineers and mechanics began to notice that it caused problems inside of car tires.
Compressed air contains water vapor, because atmospheric air always contains water. During the compression process, that water vapor can condense into a liquid, which causes major problems in car tires. The moisture in compressed air can cause rust, affect tire pressure, and fuel the growth of microbes. As reported in Popular Mechanics, a car tire can contain several quarts of water introduced by a compressed air machine.
More and more drivers are inerting their tires with nitrogen to avoid the problems caused by compressed air. Nitrogen keeps tire pressure consistent, which saves money in gas and tire maintenance. And as a dry gas, nitrogen does not introduce water into tires, keeping them strong longer.