Today, we inhale the not-so-sweet smell of real creativity. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

It was three-fifteen, March 18th, 1937. The high school at New London, Texas, was about to let out for a school holiday. Just then, without warning, the school blew up.

Three hundred people died that awful day. A 20-year-old United Press reporter named Walter Cronkite came in from Dallas. Sixty years after he walked among the mangled bodies, he still said it was the worst civilian tragedy he'd ever covered.

The explosion was the result of an undetected natural gas leak. It galvanized the public's fear of leaks.

Now, as the last survivors of that blast grow old, the American Society of Mechanical Engineers is designating a strange little device in Dallas as a National Landmark. It looks like the robot R2D2. It's a bullet-shaped metallic dome, a few feet tall. It sits next to a storage tank.

The small dome and the big tank are alone in a field. They're nothing you want to get close to. They both stink like a barrel of frightened skunks.

The little device is actually called a robot. It's the first kind of gas odorizer. It came out in 1938, just after that terrible explosion rent the sky and rent the hearts, of New London. This one was installed in 1942. It ran until 1991.

It adds two pounds of vile-smelling liquid to every million cubic feet of natural gas. It treats a half million cubic feet an hour. You see, natural gas is odorless. You can't tell when it leaks into your room. So a perfectly brilliant inventor said, "Ok, then let's give it an odor so we'll know it's there."

Today, if you smell gas, you call the repair people. Of course, it isn't really gas you smell at all. You smell one of the chemicals we use to give even a small amount of gas a nasty pungent odor.

The odorizer strikes me as the most ingenious sort of invention. It attacks the problem of safety from an unexpected side. Instead of trying to eliminate gas leakage, which would be impossible, it makes leakage evident when it occurs.

We don't worry much about natural gas explosions today. This funny, foul-smelling little engine of someone's ingenuity has delivered us from the lurking terror of a gas explosion.

Survivors of the New London blast carried the scars of that horror all their lives. For most of us, it's a forgotten horror. That's because someone turned the problem inside out and attacked it from -- within.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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The device is called The Peerless Manufacturing Metering type Gas Odorizer. The Peerless Manufacturing Company still makes odorizers. My source is a document prepared by the North Texas ASME Section. It's the official request to the ASME History and Heritage Committee for a Landmark Designation. I am grateful to Jeff Schroeter of the North Texas ASME Section for help with this episode.

I don't know who first thought of odorizing natural gas. Donald A. Sillers and Alexander Clarke hold the patent for the Peerless odorizing process.