Some thoughts here from the Compressed Gas Industry:
1) I would not consider chaining a cylinder to a tree as cylinder securement, but there are times when the options for securement are limited. I would prefer to see the cylinder strapped/chained to a cart and the two strapped/ chained to a tree in such a manner as to minimize the possibility of the cylinder falling over.
2) I agree with the assessment that the nitrogen may be being used to dry electrical or data conduit, or phone lines. that is most commonly what nitrogen cylinders are used for in these circumstances. for longterm problems with phone lines a liquid cylinder will be put in place to run a constant stream of gas over a longer period.
Nitrogen would be unlikely to use for pest control - Carbon dioxide is good for that, but unfortunately, pure CO2 can build up a static charge in the gas lines during discharge of the cylinder, which makes it less than ideal in some electrical applications.
3) The best method for moving cylidners is a cart, and cylinders should never be moved (or stored) without valve protection. While the cylinders are made to be sturdy (I've seen some in use for over 110 years with absolutely no issues) rolling them across the ground is not a very controlled method, and could potentially lead to slip/trip/fall conditions, damage to cap/valve, or damage to something else from the cylinder rolling away and hitting something.
I really doubt OSHA would be happy about that method of cylinder transport, and lifting the cylinder into the truck is also a potential source of back injuries. Much safer to use a cart and to load via lift or from a dock.
My 2 cents worth,
Airgas USA, LLC
From: Leslie Coop <lcoop**At_Symbol_Here**WILLAMETTE.EDU>
Sent: Tuesday, April 21, 2015 5:41 PM
Subject: [DCHAS-L] what to do - gas cylinder safety
A company doing work on campus chained thee nitrogen compressed gas cylinders to a tree in front of a dormitory. And left them there, for several days. Two were capped, but one of them had a regulator attached, with tubing going into a hole in the ground.
One day, two of this company's employees were seen removing one of the cylinders from the tree (one with a cap). They lay in cylinder on its side on the ground, rolled it with their feet to the curb, then rolled it off the curb and into the street to their truck. There, they picked it up by hand and manually lifted it into their truck.
Leslie Coop, MS, CCHO, CHMM
Chemical Hygiene Officer/ Stockroom Manager
Willamette University - 900 State Str - Salem, Oregon 97301