Rubber Gets Hard When Cold. Depending kind.

[SlamDunkel]

http://www.allsealsinc.com/allseals/Orings/or13.htm

As a beginner I have decided to bypass certain links and realise Silicone rubber is Synthetic to lower temperatures. That is good. My First 5 # Co2 bottle in the refrigerator was lost to either Nitrile, or another natural rubber. However the Silicone rubbers chip at room temps. If scissored.

 

[fixitoscar]

Not sure what your trying to say here, or what particular o ring failed on you.
Before you start looking at o ring material. Make sure they were the right size and that you used keg lube.

 

[SlamDunkel]

Agreed. There are food grade lubricants that are helpful. Many opt to put the regulator and bottles outside where it is most of the time warmer. Even propane regulators have been known to fail in a harsh winter environment. Some burning down houses. This was a heads up for me. I've since added a temp controller that holds the temp closer to setpoint. When I opened it it was below freezing.