Dave,

O2 sensors (if I recall correctly) are a ceramic compound, which, in the
prescence of oxygen, releases free electrons and causes a current to flow,
proportional to the oxygen content (or something along those lines).
It's  made of zirconium dioxide, coated with a gas-permeable platinum
layer.  As zirconium dioxide is used in biological implants, I don't think
that cutting it apart is going to kill you too quickly.  Just follow the
usual safety measures (safety glasses, and a dust mask wouldn't hurt!).

Keith Adams
Calgary, Alberta, Canada
1986 Vanagon GL Westfalia

Dave L wrote:

> I bought a replacement o2 sensor for my 89.  But I can't get the old
> one off - it's rusted on pretty good.  Tried using rust solvents with
> no success.  So my next step may be to saw through the sensor so the
> remaining stub is short enough for a 22mm socket on a breaker bar.
> The deepest socket I found is too short to fit over the intact unit.
>
> Thing is, I don't know what is inside the o2 sensor that makes it able
> to sense oxygen levels and I'm worried it might be some kind of cancer
> causing substance that I should not be creating clouds of.  Anyone
> know the answer ?  If it means saving my health, I'll just buy another
> catalytic converter.