Why Is There Liquid Nitrogen On The Street Corner?

Any NYC hackers may have noticed something a bit odd this summer while taking a walk… Giant tanks of the Liquid Nitrogen have been popping up around the city.

There are hoses that go from the tanks to manholes. They’re releasing the liquid nitrogen somewhere… Are they freezing sewer alligators? Fighting the Teenage Mutant Ninja Turtles? Or perhaps, cooling our phone lines??

Luckily, we now have an answer. Popular Science writer [Rebecca Harrington] got to investigate it as part of her job. As it turns out, the liquid nitrogen is being used to pressurize the cables carrying our precious phone and internet service in NYC. The cables have a protective sheath covering them, but during construction and repairs, the steam build up in some of the sewers can be too much for them — so they use liquid nitrogen expanding into gas to supplement the pressurized cables in order to keep the them dry. As the liquid nitrogen boils away, it expands 175 times which helps keep moisture out of the cables.

Sounds expensive, but apparently liquid nitrogen was the cheapest option. Helium is way too precious, liquid oxygen is combustible, and carbon dioxide is also more expensive than nitrogen. Who would have thought.

As for the public's reaction to these tanks?

While the warning signs on the tanks may seem alarming, [Bonomo] said they have never exploded or significantly leaked in the city, but they have tipped over on occasion when a car has backed into them, for instance. The cans are so sturdy that toppling hasn't caused any leaks, [Diachok] said, and Verizon technicians are able to simply stand them back up.

Did we mention the tanks also randomly release pressure by blasting liquid nitrogen into the air? It's like a little poof of snow on a hot summer's day…

In the future when everything is run through fiber optics we won't have to waste liquid nitrogen on silly things like this. Then we can get back to making our own liquid nitrogen at home in order to super-cool our Arduinos!