I have been mesmerized watching the flames through the door of my non-cat Jotul F3CB and have read everything I can find regarding exactly what is happening when I see the the little jets of secondary burn going on. Even here I have read many differing versions. This other site, http://www.chimneys.com, has the most logical explanation although not as thorough as I would like. The author says: I gather outside air enters my baffles via a secondary air port I see on the rear of the stove. This means air is exiting my baffles all the time due to the ongoing combustion process. I only see jets of combustion around these baffle holes when I have a full firebox of flames that reach up there. It is as if the flames themselves ignite the combustible gases even though it is suggested that superheated air ignites combustibles gases. I do not ever see a secondary burn take place unless flames are already up there. I would expect to see jets of secondary combustion happen whether flames were tickling up there or not since the gases should be present and the hot air is continually exiting these holes. I would expect to see jets of secondary combustion happen even more so when the flames are not actively fanning as this is when more smoke/gases are escaping. I feel like all I am seeing are hot jets of air exiting the baffles and creating a vortex through the flames that are present. I feel I should see spontaneous jets of combustion once the firebox is hot and during the first half of burning my logs when most gases are released.