You can’t see or small carbon monoxide gas but it is a potential killer. It is produced as a result of incomplete combustion.
Under normal conditions, a pure blue flame indicates complete efficient combustion. If you see orange in the flame, this indicates incomplete combustion, and the creation of carbon monoxide.
There are several possible causes of incomplete combustion, including a dirty or blocked gas jet, or insufficient ventilation.
If you see a flame like the one above (not a KOVEA stove) turn off the stove and make sure that the area that it was in is fully ventilated.
In the picture above, the middle flame is emitting carbon monoxide. Notice the orange colour.
In this case, the reason for incomplete combustion was a slightly blocked gas jet. This was solved by cleaning the gas jet with a soapy ear bud / Q-Tip.
If you have been in an enclosed space for more than a few minutes with a stove producing this kind of red/orange flame, turn off the stove, go into the fresh air and seek medical advice immediately.