Experiments on cigarettes and health

When the mixed gas is introduced, the lime water becomes turbid, indicating that there is carbon dioxide in the flue gas, and at the same time, this step also removes carbon dioxide from the original mixed gas;

Finally, limewater became turbid again after being introduced, indicating that carbon dioxide was produced when passing through hot copper oxide, so there was carbon monoxide in the original smoke.

So the answer is: there is CO2； in the smoke; Existence, ④ turbidity.