When air conditioning first appeared—a technology initially developed for use in textile factories—it was feared by many as unhealthy. So how did it make it into virtually every home in the country?

In fact, resistance to the technology came from the Open Air Movement—a major trend in thinking in the early 20th century. Supporters believed indoor air to be unhealthy, filled with CO2 that could damage our bodies, and so strongly opposed air conditioning, too.

But there was a forward-thinking group that realized that air conditioning could be useful for people: cinema owners. As movie theaters slowly adopted the technology during the 1930s and 40s, it became popular with patrons and, realizing they weren't dying, they decided to use it at home, too. Now, 80 years later, we couldn't imagine life without AC. Watch the video to find out more about the story. [Engineering Guy]