CO2 is the obvious connection here, but there's another effect at play. Candles tend to flicker in the 8Hz - 15Hz frequency range due to turbulence around the f

CO2 is the obvious connection here, but there's another effect at play. Candles tend to flicker in the 8Hz - 15Hz frequency range due to turbulence around the flame. This can be quite soporific. It's likely a neural entrainment. I wonder if LED fake candles that mimic the flicker have a similar effect.