# Power line question **URL:** \ **Category:** Factual Questions\ **Created:** [May 10, 2002, 5:29am UTC](https://boards.straightdope.com/t/power-line-question/108238 "2002-05-10T05:29:11Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [May 10, 2002, 5:29am UTC](https://boards.straightdope.com/t/power-line-question/108238/1 "2002-05-10T05:29:11Z")
Sometimes, when I’m driving and looking at the telephone poles at the side of the road, I notice a big cylinder of compressed gas with a line leading up to one of the various cables up there. Whats going on? ---
**Author:** ![octothorpe](https://avatars.discourse-cdn.com/v4/letter/o/b77776/32.png) [@octothorpe](https://boards.straightdope.com/u/octothorpe)\ **Post date:** [May 10, 2002, 5:51am UTC](https://boards.straightdope.com/t/power-line-question/108238/2 "2002-05-10T05:51:47Z")
Has nothing to do with the power lines, it is an inert gas (i believe it’s CO[sub]2[/sub], but am not certain) used in communication cables to keep them dry. Someone in the communications industry should be able to give a better explanation. # ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [May 10, 2002, 10:33am UTC](https://boards.straightdope.com/t/power-line-question/108238/3 "2002-05-10T10:33:25Z")
They use liquid N2 in NYC for underground cables to keep them dry. I have never seen one going up to an aerial cable - must be a damp location. ---
**Author:** ![femtosecond](https://avatars.discourse-cdn.com/v4/letter/f/f08c70/32.png) [@femtosecond](https://boards.straightdope.com/u/femtosecond)\ **Post date:** [May 10, 2002, 11:27am UTC](https://boards.straightdope.com/t/power-line-question/108238/4 "2002-05-10T11:27:43Z")
This thread seems related: [Liquid nitrogen canisters on sidewalk](http://boards.straightdope.com/sdmb/showthread.php?threadid=81227) ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [May 10, 2002, 6:00pm UTC](https://boards.straightdope.com/t/power-line-question/108238/5 "2002-05-10T18:00:22Z")
“They use liquid N2 in NYC for underground cables to keep them dry. I have never seen one going up to an aerial cable - must be a damp location.” - K2Dave ~ - - - Or maybe there was a flood recently! - DougC ---
**Author:** ![Belrix](https://avatars.discourse-cdn.com/v4/letter/b/ed655f/32.png) [@Belrix](https://boards.straightdope.com/u/Belrix)\ **Post date:** [May 10, 2002, 6:42pm UTC](https://boards.straightdope.com/t/power-line-question/108238/6 "2002-05-10T18:42:54Z")
In my previous years with the phone company I was surprised to find that we had lead-cable on poles. Lead cable is more accurately lead-encased cable, frequently wrapped around copper pairs that were insulated in paper. The trouble with the pole-mount stuff is that squirrels chew on it. When it rains the next time the paper insulation gets wet and the cable starts to short out. You dry it out with Nitrogen gas. Most modern cable is now plastic insulated (called PIC) and wrapped in a flexible plastic cable covering. There’s a variety that has some sort of water-repellant gel filling it for additional protection. It’s known as Icky-PIC. -B ---
**Author:** ![Belrix](https://avatars.discourse-cdn.com/v4/letter/b/ed655f/32.png) [@Belrix](https://boards.straightdope.com/u/Belrix)\ **Post date:** [May 10, 2002, 6:51pm UTC](https://boards.straightdope.com/t/power-line-question/108238/7 "2002-05-10T18:51:14Z")
\ The story was told in my building about how one of these six-foot tall, one-foot diameter cylinders dropped off a truck during the replacement process. The impact snapped the valve off the top of the cylinder. The cylinder proceeded to take off like a rocket, clearing the top of the 9-story building before starting back down. \