Someone somewhere should make it clear that the flower pot used needs to be terracotta, not the usual plastic ones you find today. So, here I am stating the obvious.

I first heard of doing this many years ago, but putting the pot on top of a natural gas fired stove's hob---supposedly a big increase in radiated heat. The stove, I think, would not produce any more CO than normal as the gas and O2 are mixed in the stove prior to burning, thus the blue flame.

I'm very skeptical of the tea candle producing any useful heat.