Ton of Thanks for Air Conditioning Pioneers


With the Summer Solstice occurring last week, it’s officially the start of summer—vacation rental rates go up, schoolkids look ahead to endless recess, and it’s definitely no longer gauche to wear white.  With the advent of summer, at least in our part of the world, comes the inevitable heat and humidity—and the singular joy of escaping it in a nicely air conditioned building.

Of all the units we use in engineering, one of the least intuitive is the “ton” that we use in the mechanical discipline.  It is a unit of energy, not a unit of mass; to understand why we use it, let’s go back first to high school chemistry, then further back to New York City at the turn of the 20th Century.

First, the chemistry.  Matter exists in three primary phases—solid, liquid, and gas (and plasma), each with greater amounts of energy.  Just as it took energy for each to move from one phase to the next in high school, the same is true for water—one of nature’s most effective carriers of heat energy.  It takes energy (a lot, it so happens) for ice to melt to water, and for water to evaporate into steam.  If you have a lot of ice—a ton (2,000 pounds)—and you let it melt over the course of 24 hours, 12,000 BTU/h will be released.  Thus, the ton of cooling.

Now, let’s step back to New York City, July 1902.  High humidity and heat were destroying sensitive inks and papers in the publishing industry.   A young engineer named Willis Carrier basically took the principles of a radiant heating system and reversed them, developing a water-based cooling system that could control the temperature and humidity of the interior environment[1].  Gives a whole new meaning to the term “hot off the presses…”

The invention quickly spread, particularly in public assembly buildings.  The movie industry and air conditioning grew up alongside one another over the next decades.  So the next time you’re sitting in the cool darkness of a movie theater, let’s give a ton of thanks to the engineers (although maybe no the movie producers) that helped make summer that little bit more bearable.


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