Magic orange peel

I was waiting on the airport, having a coffee and chatting to some tunisians when we started talking about the cold weather and heating systems here (in Tunisia) and there (Europe). Quite commonly used here for heating a room are kanun (what I’d describe as coal in a clay pot). The danger connected to them is CO2 development. So what I was told by my newly met tunisian friends was, that one puts orange peel on top of the kanun, which stops CO2 development. I later checked if I had understood correctly, but even Nasr insisted: out of experience this is what works best against the dangers of CO2. I’d really like to know how that works.