I have the Olympian 3000-unvented- w/ a quick disconnect & valve plumbed from my copper propane line.  I am still alive after 5-6 years of using it, but I always open the sliding door window & crack the skylight an inch or two.
Other than it doesn't heat the westy up quickly or keep you really warm in sub 30 degree F. temps unless I don't pop the top, it works ok.  We really only use it when not in bed, so I have never slept overnite w/ it on.  That said, the waterline does freeze w/o it on when the temp drops below 22, so I might run it on low next time I am camping in sub freezing temps.

YMMV,

Mr. BZ-not Mr. Buddy

On Nov 23, 2010, at 9:41 AM, Alistair Bell wrote:

> Hi,
> 
> i have had this little Olympian 3100 (unvented) plat. cat heater for
> about 18 years and I seldom use it - because its unvented. I know
> there is a vented version and i wonder if any listmembers have one,
> and if they do can they tell me how the venting system works and if
> it vents well.
> 
> I 'm dicking around making my own dog's breakfast vent system .
> 
> thanks
> 
> alistair