Nitrogen Tanks
I saw these nitrogen tanks on the street in Times Square; living in China has made me somewhat curious about these things, because you never knew what was going to inadvertently kill you. I assumed NYC safety standards meant these were safe, but I was still curious about them.
Googling reveals they are used to keep underground phone cables dry. The nitrogen drives out moisture. Who knew? (Not me, I failed high school chemistry.)
Comments
Specifically, they're used with phone lines that use paper insulation.
While the outer "shell" has always been waterproof, it was only in the 1960s(?) they started using plastic insulation on the inside wires. Before, with paper, condensation inside the outer shell of the cable would cause the paper to become damp and create shorts.
Nitrogen doesn't have the moisture in it like air, so it's used to dry out the lines.
(Dad worked for the phone company and I asked him when I was little why there were bottles strapped to telephone poles sometimes)
Very interesting info, thanks!