On 01/12/2018 16:18, alan_m wrote:
On 01/12/2018 16:05, Roger Hayter wrote:

Very old ones might
use highly carcinogenic oils I've forgotten the name of (but not
inflammable, also used for potting transfomers many years ago), and
apparently in the USA sometimes vegetable oils have been used.


Oil filled transformers do explode!
https://www.youtube.com/watch?v=fzbQjd_Oo4Q


Indeed, though that is from arcing inside followed by release of oil
sprays into the atmosphere. There is a *lot* of external energy being
supplied to a transformer.

Going back to the OPs suggestion, I don't believe you will get an oxygen
rich atmosphere inside in the scenario he describes. With air and oil on
a hot element, the oil will oxidise, and "getter" the oxygen.