The Air-conditioned Century

PrintPrintEmailEmail

IN THE SUMMER of 1881, as James Garfield lay dying of an assassin’s bullet in the White House, a team of naval engineers was called in to solve a vexing problem: how to cool the President’s bedroom. The temperature in Washington was hovering above ninety, and the humidity was uncomfortably high.

Within a week of the shooting, working virtually around the clock, the engineers had rigged up a contraption that provided some relief. It consisted of a large cast-iron box, about the size of a coffin, which contained dozens of screens, each made of a thin layer of terry-cloth cotton. On top of this box was a tank holding more than half a ton of shaved ice, salt, and water. As the ice melted, it turned into a briny slush, which trickled down onto the terry-cloth screens. A fan at one end of the lower box sucked in air from the outside, which was cooled as it passed across the screens and was then pumped through a duct into the President s bedroom.

After making a number of refinements to control the incessant clatter of the machine and the moisture content of the air it produced—at first the humidity in the room actually increased—the engineers finally succeeded. The temperature in the sickroom dropped twenty degrees, and the air was noticeably drier than outside. Of course, these conditions were not achieved without considerable effort: during the fifty-eight days that the apparatus was cooling the President, it consumed over half a million pounds of ice. In the end Garfield s doctors allowed their mortally wounded patient to escape the enervating Washington heat by removing him to the New Jersey shore.

Nevertheless, the naval engineers were pleased with the results of their experiments. “This field of study,” they noted in their report, “presents great opportunities for effecting a better condition of the atmosphere of our rooms… . Hospitals and public buildings ought to he especially protected from the evil results attending a vitiated condition of the air, and we can see no reason why their atmosphere may not be made comfortable and healthful at all seasons and under all conditions of the outside air.”

 
The 1881 White House “air conditioner” used more than four tons of ice a day just to cool one room.

Twenty-one years were to pass before what is now considered the first real air-conditioning apparatus was installed by Willis Haviland Carrier in a Brooklyn printing plant; another twelve before the first hospital ward was air-conditioned; ten more before the first department store was mechanically cooled; and seventy years in all before the vision of President Garfield’s attending engineers was fully realized.

Although we now take for granted what can be accomplished with a flick of a switch, the ability to control indoor environment was, only a hundred years ago, still beyond the reach of technology. The experiments at the White House in the summer of 1881 notwithstanding, a practical solution to the problem of regulating both the temperature and the moisture content of air remained as elusive as ever. A system that required the melting of several tons of ice a day to cool just one room was an extravagance that only the very rich or the very powerful could afford.

 

And even then there was no guarantee of comfort, because air passing through damp cloth or over melting ice absorbs moisture from evaporating water. As ingenious as men had been in devising ways to cool themselves—an eighth-century Baghdad caliph packed imported snow between the double walls of his summer villa, and Leonardo da Vinci designed a water-driven fan to cool the boudoir of his patron’s wife—no one had figured out how to conquer humidity, short of picking up and moving to a drier climate.

The simple reason was that the precise relationship between temperature and moisture was not understood before Carrier. The clue had been staring people in the face for centuries—every time drops of moisture condensed on the outside of a glass of ice water—but until Willis Carrier had his epiphany on a cold, foggy night in a Pittsburgh train station in the fall of 1902, the trick of reducing humidity to a desired level and holding it there had not been mastered. Carrier was only twenty-five, just a year and a half out of Cornell University. What he saw on that fog-shrouded night was the fundamental principle upon which the air-conditioning industry was later built, a concept so simple and yet so paradoxical that no one had seen it before: it was possible, he realized, to dry air by saturating it with water.

Carrier’s solution to the problem of humidity control, which he patented four years later as his “Apparatus for Treating Air,” was to create an artificial fog by spraying a fine mist of water into a box, thereby saturating the air inside. By adjusting the temperature of the water spray, he could control the temperature of the air and, since cold air was known to hold less moisture than warm air, regulate the humidity as well. In effect he was able to wring the excess moisture out of the air passing through his apparatus by using the water particles from the spray as a condensing surface. And he could do it with precision, achieving any level of humidity desired.