Cotton begins to oxidize at 95C. http://www.mcclureindustries.com/Reports/Spontaneous_Ignition.pdf What does it give off at over twice that temp? Of course it's not toxic like asbestos, but still, I do wonder if there should be any concern with this? I just find it kind of odd that we lust over an all glass vapor path, but don't think twice about introducing a wad of cotton in that all glass vapor path. But hey, I look at things a bit askew at times. Kinda my nature.